diff --git a/Gemfile.lock b/Gemfile.lock
index 43820f9ea..07b02673b 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -270,7 +270,6 @@ DEPENDENCIES
   newrelic_rpm
   paperclip (~> 4.3)
   pdfkit (~> 0.6.2)
-  paperclip (~> 4.3)
   pg (~> 0.17.0)
   pghero
   poltergeist (~> 1.5.0)
diff --git a/app/controllers/assistants_controller.rb b/app/controllers/assistants_controller.rb
index 71edbca1a..1575ff4e2 100644
--- a/app/controllers/assistants_controller.rb
+++ b/app/controllers/assistants_controller.rb
@@ -34,7 +34,7 @@ def destroy
   private
 
   def set_course
-    @course = Course.find_by id: params[:course_id]
+    @course = Course.find_by! name: params[:course_name]
   end
 
   def assistant_params
diff --git a/app/controllers/breadcrumb_helpers.rb b/app/controllers/breadcrumb_helpers.rb
index e048b201b..efbbe075e 100644
--- a/app/controllers/breadcrumb_helpers.rb
+++ b/app/controllers/breadcrumb_helpers.rb
@@ -14,9 +14,9 @@ def add_course_breadcrumb
 
   def add_exercise_breadcrumb
     if @exercise
-      add_breadcrumb "Exercise #{@exercise.name}", exercise_path(@exercise)
+      add_breadcrumb "Exercise #{@exercise.name}", organization_course_exercise_path(@organization, @course, @exercise)
     elsif @submission && @submission.exercise
-      add_breadcrumb "Exercise #{@submission.exercise.name}", exercise_path(@submission.exercise)
+      add_breadcrumb "Exercise #{@submission.exercise.name}", organization_course_exercise_path(@organization, @course, @submission.exercise)
     elsif @submission && @submission.exercise_name
       add_breadcrumb "(deleted exercise #{@submission.exercise_name}"
     else
diff --git a/app/controllers/course_notifications_controller.rb b/app/controllers/course_notifications_controller.rb
index 26671b679..fde61fc10 100644
--- a/app/controllers/course_notifications_controller.rb
+++ b/app/controllers/course_notifications_controller.rb
@@ -3,16 +3,16 @@ class CourseNotificationsController < ApplicationController
   before_action :set_organization
 
   def new
-    course = Course.find(course_notification_params[:course_id])
+    course = Course.find_by!(name: course_notification_params[:course_name])
     authorize! :send_mail_to_participants, course
     @notifier ||= CourseNotification.new
-    @course = Course.find_by(id: params[:course_id])
+    @course = Course.find_by!(name: params[:course_name], organization: @organization)
     add_course_breadcrumb
     add_breadcrumb 'Course notification'
   end
 
   def create
-    course = Course.find(course_notification_params[:course_id])
+    course = Course.find_by!(name: course_notification_params[:course_name])
     authorize! :send_mail_to_participants, course
 
     participants = User.course_students(course)
@@ -48,10 +48,10 @@ def create
   private
 
   def course_notification_params
-    params.permit(:commit, :course_id, course_notification: [:topic, :message])
+    params.permit(:commit, :course_name, course_notification: [:topic, :message])
   end
 
   def set_organization
-    @organization = Organization.find_by(slug: params[:organization_id])
+    @organization = Organization.find_by!(slug: params[:organization_id])
   end
 end
diff --git a/app/controllers/courses_controller.rb b/app/controllers/courses_controller.rb
index b270b0de2..1a94bf781 100644
--- a/app/controllers/courses_controller.rb
+++ b/app/controllers/courses_controller.rb
@@ -60,7 +60,7 @@ def show
 
   # Method for teacher to give a single course for students to select.
   def show_json
-    course = [Course.find(params[:id])]
+    course = [Course.find_by!(name: params[:name])]
     authorize! :read, course
     return respond_access_denied('Authentication required') if current_user.guest?
 
@@ -166,7 +166,7 @@ def save_deadlines
   end
 
   def help
-    @course = Course.find(params[:course_id])
+    @course = Course.find_by!(name: params[:course_name])
     authorize! :read, @course
     add_course_breadcrumb
     add_breadcrumb 'Help page'
@@ -245,11 +245,12 @@ def assign_show_view_vars
   end
 
   def set_organization
-    @organization = Organization.find_by(slug: params[:organization_id])
+    @organization ||= Organization.find_by!(slug: params[:organization_id])
   end
 
   def set_course
-    @course = Course.find(params[:id])
+    @organization ||= Organization.find_by!(slug: params[:organization_id])
+    @course = Course.find_by!(name: params[:name], organization: @organization)
   end
 
   def group_params
diff --git a/app/controllers/emails_controller.rb b/app/controllers/emails_controller.rb
index 822ec1aed..8f92297f9 100644
--- a/app/controllers/emails_controller.rb
+++ b/app/controllers/emails_controller.rb
@@ -2,9 +2,9 @@
 class EmailsController < ApplicationController
   def index
     organization_id = params[:organization_id]
-    course_id = params[:id]
+    course_name = params[:name]
 
-    if organization_id && course_id
+    if organization_id && course_name
       index_course
     else
       index_global
@@ -26,8 +26,8 @@ def index_global
   end
 
   def index_course
-    @course = Course.find(params[:id])
-    @organization = @course.organization
+    @organization = Organization.find_by!(slug: params[:organization_id])
+    @course = Course.find_by!(name: params[:name], organization: @organization)
 
     authorize! :list_user_emails, @course
 
diff --git a/app/controllers/exercise_status_controller.rb b/app/controllers/exercise_status_controller.rb
index 9a7d989da..8013e47d5 100644
--- a/app/controllers/exercise_status_controller.rb
+++ b/app/controllers/exercise_status_controller.rb
@@ -2,10 +2,10 @@ class ExerciseStatusController < ApplicationController
   skip_authorization_check
 
   def show
-    course_id = params[:course_id]
+    course_name = params[:course_name]
     user_id = params[:id]
 
-    course = Course.where(id: course_id).first || Course.where(name: course_id).first
+    course = Course.where(id: course_name).first || Course.where(name: course_name).first
     user = User.where(id: user_id).first || User.where(login: user_id).first
 
     return respond_access_denied unless course.visible_to?(Guest.new) || current_user.administrator?
diff --git a/app/controllers/exercises_controller.rb b/app/controllers/exercises_controller.rb
index 821b5dfaa..19bf894b2 100644
--- a/app/controllers/exercises_controller.rb
+++ b/app/controllers/exercises_controller.rb
@@ -1,8 +1,7 @@
 class ExercisesController < ApplicationController
+  before_action :set_params, only: [:show]
+
   def show
-    @exercise = Exercise.find(params[:id])
-    @course = Course.lock('FOR SHARE').find(@exercise.course_id)
-    @organization = @course.organization
     authorize! :read, @course
     authorize! :read, @exercise
 
@@ -55,8 +54,8 @@ def show
   end
 
   def set_disabled_statuses
-    @course = Course.find(params[:course_id])
-    @organization = @course.organization
+    @organization = Organization.find_by!(slug: params[:organization_id])
+    @course = Course.find_by!(name: params[:course_name], organization: @organization)
     authorize! :teach, @organization
 
     selected_exercise_ids = params[:course][:exercises]
@@ -71,4 +70,12 @@ def set_disabled_statuses
     redirect_to manage_exercises_organization_course_path(@organization, @course),
                 notice: 'Exercises successfully updated.'
   end
+
+  private
+
+  def set_params
+    @organization = Organization.find_by!(slug: params[:organization_id])
+    @course = Course.lock('FOR SHARE').find_by!(name: params[:course_name], organization: @organization)
+    @exercise = Exercise.find_by!(name: params[:name], course: @course)
+  end
 end
diff --git a/app/controllers/feedback_answers_charts_controller.rb b/app/controllers/feedback_answers_charts_controller.rb
index 397b5320e..efdb94090 100644
--- a/app/controllers/feedback_answers_charts_controller.rb
+++ b/app/controllers/feedback_answers_charts_controller.rb
@@ -1,7 +1,7 @@
 class FeedbackAnswersChartsController < ApplicationController
   def show
-    @course = Course.find(params[:course_id])
-    @organization = @course.organization
+    @organization = Organization.find_by!(slug: params[:organization_id])
+    @course = Course.find_by!(name: params[:course_name], organization: @organization)
 
     authorize! :read_feedback_questions, @course
     authorize! :read_feedback_answers, @course
diff --git a/app/controllers/feedback_answers_controller.rb b/app/controllers/feedback_answers_controller.rb
index d3cb0b5e2..019308de8 100644
--- a/app/controllers/feedback_answers_controller.rb
+++ b/app/controllers/feedback_answers_controller.rb
@@ -1,15 +1,17 @@
 class FeedbackAnswersController < ApplicationController
   def index
-    if params[:course_id]
-      @course = Course.find(params[:course_id])
+    @organization = Organization.find_by!(slug: params[:organization_id])
+
+    if params[:course_name] && !params[:exercise_name]
+      @course = Course.find_by!(name: params[:course_name], organization: @organization)
       @parent = @course
       @numeric_stats = @course.exercises.where(hidden: false).sort.map do |ex|
         [ex, FeedbackAnswer.numeric_answer_averages(ex), ex.submissions_having_feedback.count]
       end
       @title = @course.name
-    elsif params[:exercise_id]
-      @exercise = Exercise.find(params[:exercise_id])
-      @course = @exercise.course
+    elsif params[:exercise_name]
+      @course = Course.find_by!(name: params[:course_name], organization: @organization)
+      @exercise = Exercise.find_by!(name: params[:exercise_name], course: @course)
       @parent = @exercise
       @numeric_stats = [[@exercise, FeedbackAnswer.numeric_answer_averages(@exercise), @exercise.submissions_having_feedback.count]]
       @title = @exercise.name
@@ -17,11 +19,10 @@ def index
       return respond_not_found
     end
 
-    @organization = @course.organization
     add_course_breadcrumb
     if @exercise
       add_exercise_breadcrumb
-      add_breadcrumb 'Feedback', exercise_feedback_answers_path(@exercise)
+      add_breadcrumb 'Feedback', organization_course_exercise_feedback_answers_path(@organization, @course, @exercise)
     else
       add_breadcrumb 'Feedback', organization_course_feedback_answers_path
     end
diff --git a/app/controllers/feedback_questions_controller.rb b/app/controllers/feedback_questions_controller.rb
index b75994794..d54515b44 100644
--- a/app/controllers/feedback_questions_controller.rb
+++ b/app/controllers/feedback_questions_controller.rb
@@ -1,7 +1,6 @@
 # Handles the feedback question editing UI.
 class FeedbackQuestionsController < ApplicationController
-  before_action :set_course
-  before_action :set_organization
+  before_action :set_params, only: [:index, :create, :new]
 
   def index
     add_course_breadcrumb
@@ -85,8 +84,9 @@ def feedback_question_params
     params.permit({ feedback_question: [:question, :title, :kind] }, :intrange_min, :intrange_max, :commit, :course_id)
   end
 
-  def set_course
-    @course = Course.find(params[:course_id]) if params[:course_id]
+  def set_params
+    @organization = Organization.find_by!(slug: params[:organization_id])
+    @course = Course.find_by!(name: params[:course_name], organization: @organization) if params[:course_name]
     authorize! :read, @course
   end
 
@@ -94,8 +94,4 @@ def fix_question_kind(question)
     return unless question.kind == 'intrange'
     question.kind += "[#{params[:intrange_min]}..#{params[:intrange_max]}]"
   end
-
-  def set_organization
-    @organization = Organization.find_by(slug: params[:organization_id])
-  end
 end
diff --git a/app/controllers/organizations_controller.rb b/app/controllers/organizations_controller.rb
index e640ea6dc..17efa6cca 100644
--- a/app/controllers/organizations_controller.rb
+++ b/app/controllers/organizations_controller.rb
@@ -119,8 +119,7 @@ def percent_completed_hash(courses, user)
   end
 
   def set_organization
-    @organization = Organization.find_by(slug: params[:id])
-    fail ActiveRecord::RecordNotFound, 'Invalid organization id' if @organization.nil?
+    @organization = Organization.find_by!(slug: params[:id])
   end
 
   def organization_params
diff --git a/app/controllers/points_controller.rb b/app/controllers/points_controller.rb
index c1c147c58..6a0a4c9dd 100644
--- a/app/controllers/points_controller.rb
+++ b/app/controllers/points_controller.rb
@@ -5,7 +5,7 @@ class PointsController < ApplicationController
   before_action :set_organization
 
   def index
-    @course = Course.find(params[:course_id])
+    @course = Course.find_by!(name: params[:course_name], organization: @organization)
     authorize! :see_points, @course
     add_course_breadcrumb
     add_breadcrumb 'Points'
@@ -27,13 +27,13 @@ def index
   def refresh_gdocs
     authorize! :refresh, @course
     @sheetname = params[:id]
-    @course = Course.find(params[:course_id])
+    @course = Course.find_by!(name: params[:course_name], organization: @organization)
     @notifications = @course.refresh_gdocs_worksheet @sheetname
   end
 
   def show
     @sheetname = params[:id]
-    @course = Course.find(params[:course_id])
+    @course = Course.find_by!(name: params[:course_name], organization: @organization)
     authorize! :see_points, @course
 
     add_course_breadcrumb
@@ -110,6 +110,6 @@ def sort_summary(summary, sorting)
   end
 
   def set_organization
-    @organization = Organization.find_by(slug: params[:organization_id])
+    @organization = Organization.find_by!(slug: params[:organization_id])
   end
 end
diff --git a/app/controllers/reviewed_submissions_controller.rb b/app/controllers/reviewed_submissions_controller.rb
index 63f6a9dd9..0df101940 100644
--- a/app/controllers/reviewed_submissions_controller.rb
+++ b/app/controllers/reviewed_submissions_controller.rb
@@ -2,8 +2,8 @@
 class ReviewedSubmissionsController < ApplicationController
   
   def index
-    @course = Course.find(params[:course_id])
-    @organization = @course.organization
+    @organization = Organization.find_by!(slug: params[:organization_id])
+    @course = Course.find_by!(name: params[:course_name], organization: @organization)
     authorize! :teach, @course
     add_course_breadcrumb
     add_breadcrumb 'Code reviews', organization_course_reviews_path(@organization, @course)
diff --git a/app/controllers/reviews_controller.rb b/app/controllers/reviews_controller.rb
index 12b6b36f3..ad9755e1b 100644
--- a/app/controllers/reviews_controller.rb
+++ b/app/controllers/reviews_controller.rb
@@ -5,9 +5,8 @@ class ReviewsController < ApplicationController
   before_action :set_organization, except: [:new, :create]
 
   def index
-    if params[:course_id]
+    if params[:course_name]
       fetch :course
-      @organization = @course.organization
       @my_reviews = @course.submissions
         .where(user_id: current_user.id)
         .where('requests_review OR requires_review OR reviewed')
@@ -201,7 +200,7 @@ def mark_as_reviewed
 
   def fetch(*stuff)
     if stuff.include? :course
-      @course = Course.find(params[:course_id])
+      @course = Course.find_by!(name: params[:course_name], organization: @organization)
       authorize! :read, @course
     end
     if stuff.include? :submission
@@ -265,6 +264,6 @@ def award_points
   private
 
   def set_organization
-    @organization = Organization.find_by(slug: params[:organization_id])
+    @organization = Organization.find_by!(slug: params[:organization_id])
   end
 end
diff --git a/app/controllers/solutions_controller.rb b/app/controllers/solutions_controller.rb
index eb6d0ab9c..7593c86a7 100644
--- a/app/controllers/solutions_controller.rb
+++ b/app/controllers/solutions_controller.rb
@@ -1,13 +1,13 @@
 # Returns the suggestion solution as a ZIP.
 class SolutionsController < ApplicationController
   def show
-    @exercise = Exercise.find(params[:exercise_id])
-    @course = @exercise.course
-    @organization = @course.organization
+    @organization = Organization.find_by!(slug: params[:organization_id])
+    @course = Course.find_by!(name: params[:course_name], organization: @organization)
+    @exercise = Exercise.find_by!(name: params[:exercise_name], course: @course)
 
     add_course_breadcrumb
     add_exercise_breadcrumb
-    add_breadcrumb 'Suggested solution'
+    add_breadcrumb 'Suggested solution', organization_course_exercise_solution_path(@organization, @course, @exercise)
 
     @solution = @exercise.solution
     begin
diff --git a/app/controllers/stats_controller.rb b/app/controllers/stats_controller.rb
index e79146704..3a26c2a0c 100644
--- a/app/controllers/stats_controller.rb
+++ b/app/controllers/stats_controller.rb
@@ -36,8 +36,8 @@ def show
   private
 
   def get_vars
-    if params[:course_id]
-      @course = Course.find(params[:course_id])
+    if params[:course_name]
+      @course = Course.find_by!(name: params[:course_name], organization: @organization)
     end
   end
 
@@ -168,6 +168,6 @@ def param_as_one_of(name, valid_values)
   private
 
   def set_organization
-    @organization = Organization.find_by(slug: params[:organization_id])
+    @organization = Organization.find_by!(slug: params[:organization_id])
   end
 end
diff --git a/app/controllers/submissions_controller.rb b/app/controllers/submissions_controller.rb
index 78fec2186..67e42d69e 100644
--- a/app/controllers/submissions_controller.rb
+++ b/app/controllers/submissions_controller.rb
@@ -4,12 +4,13 @@
 # Also handles rerun requests.
 class SubmissionsController < ApplicationController
   around_action :course_transaction
-  before_action :get_course_and_exercise
 
   # Manually checked for #show and index
   skip_authorization_check only: [:show, :index]
 
   def index
+    set_course
+
     respond_to do |format|
       format.json do
         if params[:row_format] == 'datatables'
@@ -27,9 +28,12 @@ def index
   end
 
   def show
-    @course ||= @submission.course
-    @exercise ||= @submission.exercise
-    @organization = @course.organization
+    if params[:paste_key]
+      return unless set_paste
+    else
+      set_submission
+    end
+
     add_course_breadcrumb
     add_exercise_breadcrumb
     add_submission_breadcrumb
@@ -52,7 +56,7 @@ def show
           points: @submission.points_list,
           validations: @submission.validations,
           valgrind: @submission.valgrind,
-          solution_url: @exercise.solution.visible_to?(current_user) ? view_context.exercise_solution_url(@exercise) : nil,
+          solution_url: @exercise.solution.visible_to?(current_user) ? view_context.organization_course_exercise_solution_url(@organization, @course, @exercise) : nil,
           submitted_at: @submission.created_at,
           processing_time: @submission.processing_time,
           reviewed: @submission.reviewed?,
@@ -95,6 +99,8 @@ def show
   end
 
   def create
+    set_exercise
+
     if !params[:submission] || !params[:submission][:file]
       return respond_not_found('No ZIP file selected or failed to receive it')
     end
@@ -148,7 +154,7 @@ def create
           redirect_to(submission_path(@submission),
                       notice: 'Submission received.')
         else
-          redirect_to(exercise_path(@exercise),
+          redirect_to(organization_course_exercise_path(@organization, @course, @exercise),
                       alert: errormsg)
         end
       end
@@ -164,6 +170,8 @@ def create
   end
 
   def update
+    set_submission
+
     submission = Submission.find(params[:id]) || respond_not_found
     authorize! :update, submission
     if params[:rerun]
@@ -180,10 +188,12 @@ def update
   end
 
   def update_by_exercise
+    set_exercise(:name)
+
     for submission in @exercise.submissions
       schedule_for_rerun(submission, -2)
     end
-    redirect_to exercise_path(@exercise), notice: 'Reruns scheduled'
+    redirect_to organization_course_exercise_path(@organization, @course, @exercise), notice: 'Reruns scheduled'
   end
 
   private
@@ -194,31 +204,35 @@ def course_transaction
     end
   end
 
-  # Ugly manual access control :/
-  def get_course_and_exercise
-    if params[:id]
-      @submission = Submission.find(params[:id])
-      authorize! :read, @submission
-      @course = @submission.course
-      @exercise = @submission.exercise
-    elsif params[:exercise_id]
-      @exercise = Exercise.find(params[:exercise_id])
-      @course = Course.lock('FOR SHARE').find(@exercise.course_id)
-      authorize! :read, @course
-      authorize! :read, @exercise
-    elsif params[:paste_key]
-      @submission = Submission.find_by_paste_key!(params[:paste_key])
-      @exercise = @submission.exercise
-      @course = @exercise.course
-      @is_paste = true
-      check_access!
-    elsif params[:course_id]
-      @course = Course.lock('FOR SHARE').find(params[:course_id])
-      @organization = @course.organization
-      authorize! :read, @course
-    else
-      respond_access_denied
-    end
+  def set_submission
+    @submission = Submission.find(params[:id])
+    @exercise = @submission.exercise
+    @course = @submission.course
+    @organization = @course.organization
+    authorize! :read, @submission
+  end
+
+  def set_exercise(param_name = :exercise_name)
+    @organization = Organization.find_by!(slug: params[:organization_id])
+    @course = Course.lock('FOR SHARE').find_by!(name: params[:course_name], organization: @organization)
+    @exercise = Exercise.find_by!(name: params[param_name], course: @course)
+    authorize! :read, @course
+    authorize! :read, @exercise
+  end
+
+  def set_course
+    @organization = Organization.find_by!(slug: params[:organization_id])
+    @course = Course.lock('FOR SHARE').find_by!(name: params[:course_name], organization: @organization)
+    authorize! :read, @course
+  end
+
+  def set_paste
+    @submission = Submission.find_by_paste_key!(params[:paste_key])
+    @exercise = @submission.exercise
+    @course = @submission.course
+    @organization = @course.organization
+    @is_paste = true
+    check_access!
   end
 
   def schedule_for_rerun(submission, priority)
@@ -266,13 +280,16 @@ def index_json_datatables
 
   def check_access!
     paste_visibility = @course.paste_visibility || 'open'
+    can_access = true
     case paste_visibility
     when 'protected'
-      respond_access_denied unless can?(:teach, @course) || @submission.user_id.to_s == current_user.id.to_s || (@submission.public? && @submission.exercise.completed_by?(current_user))
+      can_access = false unless can?(:teach, @course) || @submission.user_id.to_s == current_user.id.to_s || (@submission.public? && @submission.exercise.completed_by?(current_user))
     when 'no-tests-public'
-      respond_access_denied unless @submission.created_at > 2.hours.ago
+      can_access = false unless @submission.created_at > 2.hours.ago
     else
-      respond_access_denied unless can?(:teach, @course) || @submission.user_id.to_s == current_user.id.to_s || (@submission.public? && @submission.created_at > 2.hours.ago)
+      can_access = false unless can?(:teach, @course) || @submission.user_id.to_s == current_user.id.to_s || (@submission.public? && @submission.created_at > 2.hours.ago)
     end
+    respond_access_denied unless can_access
+    can_access
   end
 end
diff --git a/app/controllers/teachers_controller.rb b/app/controllers/teachers_controller.rb
index 929402077..23256839f 100644
--- a/app/controllers/teachers_controller.rb
+++ b/app/controllers/teachers_controller.rb
@@ -35,7 +35,7 @@ def destroy
   private
 
   def set_organization
-    @organization = Organization.find_by(slug: params[:organization_id])
+    @organization = Organization.find_by!(slug: params[:organization_id])
   end
 
   def teacher_params
diff --git a/app/controllers/unlocks_controller.rb b/app/controllers/unlocks_controller.rb
index 34581eaae..f80c7f21b 100644
--- a/app/controllers/unlocks_controller.rb
+++ b/app/controllers/unlocks_controller.rb
@@ -1,9 +1,9 @@
 # Receives explicit unlock requests and shows a web UI for making them.
 class UnlocksController < ApplicationController
   def show
-    @course = Course.find(params[:course_id])
+    @organization = Organization.find_by!(slug: params[:organization_id])
+    @course = Course.find_by!(name: params[:course_name], organization: @organization)
     authorize! :read, @course
-    @organization = Organization.find_by(slug: params[:organization_id])
     @exercises = @course.unlockable_exercises_for(current_user)
 
     respond_to do |format|
@@ -15,9 +15,9 @@ def show
   end
 
   def create
-    @course = Course.find(params[:course_id])
+    @organization = Organization.find_by!(slug: params[:organization_id])
+    @course = Course.find_by!(name: params[:course_name], organization: @organization)
     authorize! :read, @course
-    @organization = Organization.find_by(slug: params[:organization_id])
     @exercises = @course.unlockable_exercises_for(current_user)
 
     Unlock.unlock_exercises(@exercises, current_user)
diff --git a/app/helpers/exercises_helper.rb b/app/helpers/exercises_helper.rb
index 50a5167c5..adee3c1ca 100644
--- a/app/helpers/exercises_helper.rb
+++ b/app/helpers/exercises_helper.rb
@@ -1,10 +1,10 @@
 module ExercisesHelper
   def exercise_zip_url(e)
-    "#{exercise_url(e, format: 'zip')}"
+    "#{organization_course_exercise_url(e.course.organization, e.course, e, format: 'zip')}"
   end
 
   def exercise_solution_zip_url(e)
-    "#{exercise_solution_url(e, format: 'zip')}"
+    "#{organization_course_exercise_solution_url(e.course.organization, e.course, e, format: 'zip')}"
   end
 
   def green(percentage)
diff --git a/app/helpers/submissions_helper.rb b/app/helpers/submissions_helper.rb
index 4c0a69aa3..bb4460d6b 100644
--- a/app/helpers/submissions_helper.rb
+++ b/app/helpers/submissions_helper.rb
@@ -88,9 +88,12 @@ def submissions_for_datatables(submissions)
   end
 
   def link_to_submission_exericse(submission, text = nil, missing_text = '')
-    if submission.exercise
-      text = submission.exercise.name if text.nil?
-      link_to text, exercise_path(submission.exercise)
+    exercise = submission.exercise
+    if exercise
+      course = exercise.course
+      organization = course.organization
+      text = exercise.name if text.nil?
+      link_to text, organization_course_exercise_path(organization, course, exercise)
     else
       missing_text
     end
diff --git a/app/models/course.rb b/app/models/course.rb
index 1612f0f64..2b83f2edf 100644
--- a/app/models/course.rb
+++ b/app/models/course.rb
@@ -396,6 +396,10 @@ def contains_unlock_deadlines?
     exercise_groups.any? { |group| group.contains_unlock_deadlines?}
   end
 
+  def to_param
+    name
+  end
+
   def material_url=(material)
     return super('') if material.blank?
     unless material =~ /^https?:\/\//
diff --git a/app/models/exercise.rb b/app/models/exercise.rb
index ec979650a..261c7f996 100644
--- a/app/models/exercise.rb
+++ b/app/models/exercise.rb
@@ -368,6 +368,10 @@ def self.count_completed(users, exercises)
     end
   end
 
+  def to_param
+    name
+  end
+
   private
 
   def new_deadline_spec_obj(spec)
diff --git a/app/views/courses/show.html.erb b/app/views/courses/show.html.erb
index b8b77aa35..af8b96ebf 100644
--- a/app/views/courses/show.html.erb
+++ b/app/views/courses/show.html.erb
@@ -156,7 +156,7 @@
     </div>
 
     <% if signed_in? %>
-        <div class="alternative-format-links">[<%= link_to 'json', "#{one_course_json_organization_course_path organization_id: @organization.slug, id: @course.id, api_version: ApiVersion::API_VERSION}" %>]</div>
+        <div class="alternative-format-links">[<%= link_to 'json', "#{one_course_json_organization_course_path organization_id: @organization.slug, id: @course.name, api_version: ApiVersion::API_VERSION}" %>]</div>
     <% end %>
 
     <h2>All exercises</h2>
diff --git a/app/views/exercises/_list_single.html.erb b/app/views/exercises/_list_single.html.erb
index d5d7ff858..4fc8aba06 100644
--- a/app/views/exercises/_list_single.html.erb
+++ b/app/views/exercises/_list_single.html.erb
@@ -1,4 +1,4 @@
-<%= link_to exercise.name, exercise %>
+<%= link_to exercise.name, organization_course_exercise_path(@organization, @course, exercise) %>
 <%
    notes = []
    notes << 'hidden' if exercise.hidden?
diff --git a/app/views/exercises/show.html.erb b/app/views/exercises/show.html.erb
index 5fe6a722c..2b27da4d5 100644
--- a/app/views/exercises/show.html.erb
+++ b/app/views/exercises/show.html.erb
@@ -68,11 +68,11 @@
   <% end %>
 
   <% if @exercise.solution && can?(:read, @exercise.solution) %>
-    <li><%= link_to 'View suggested solution', exercise_solution_path(@exercise) %></li>
+    <li><%= link_to 'View suggested solution', organization_course_exercise_solution_path(@organization, @course, @exercise) %></li>
   <% end %>
 
   <% if can? :read, FeedbackAnswer %>
-    <li><%= link_to 'View feedback', exercise_feedback_answers_path(@exercise) %></li>
+    <li><%= link_to 'View feedback', organization_course_exercise_feedback_answers_path(@organization, @course, @exercise) %></li>
   <% end %>
 </ul>
 
@@ -110,7 +110,11 @@
         end
       %>
       <br>
-      <%= button_to 'Rerun all submissions', exercise_update_submissions_path(@exercise), :method => :put, :confirm => confirm_msg, class: "btn btn-danger"%>
+      <%=
+          button_to 'Rerun all submissions',
+                    update_submissions_organization_course_exercise_path(@organization, @course, @exercise),
+                    method: :put, confirm: confirm_msg, class: "btn btn-danger"
+      %>
       (may add points; never deletes points; may take a long time)
     </div>
   </div>
diff --git a/app/views/feedback_answers/_numeric_feedback.html.erb b/app/views/feedback_answers/_numeric_feedback.html.erb
index a6ce11634..1603c07e2 100644
--- a/app/views/feedback_answers/_numeric_feedback.html.erb
+++ b/app/views/feedback_answers/_numeric_feedback.html.erb
@@ -12,7 +12,7 @@
     <% for exercise, averages, answer_count in stats %>
       <% if answer_count > 0 %>
         <tr>
-          <td><%= link_to exercise.name, exercise %></td>
+          <td><%= link_to exercise.name, organization_course_exercise_url(exercise.course.organization, exercise.course, exercise) %></td>
           <% for question in questions %>
             <td><%= if averages[question.id] then sprintf("%.2f", averages[question.id]) else '-' end %></td>
           <% end %>
@@ -26,7 +26,7 @@
 <% if parent.is_a?(Course) %>
   <div class="alternative-format-links">[<%= link_to "json", "#{organization_course_feedback_answers_path @organization, @parent, :format => :json}" %>]</div>
 <% elsif parent.is_a?(Exercise) %>
-  <div class="alternative-format-links">[<%= link_to "json", "#{organization_exercise_feedback_answers_path @organization, @parent, :format => :json}" %>]</div>
+  <div class="alternative-format-links">[<%= link_to "json", "#{organization_course_exercise_feedback_answers_path @organization, @parent.course, @parent, :format => :json}" %>]</div>
 <% end %>
 
 <div class="footnote">
diff --git a/app/views/feedback_answers/_text_feedback.html.erb b/app/views/feedback_answers/_text_feedback.html.erb
index f4bc4d581..7d17d7323 100644
--- a/app/views/feedback_answers/_text_feedback.html.erb
+++ b/app/views/feedback_answers/_text_feedback.html.erb
@@ -9,7 +9,7 @@
       <% end %>
       with <%= link_to "submission ##{answer.submission.id}", answer.submission %>
       <% unless @exercise %>
-        for <%= link_to answer.exercise.name, answer.exercise %>
+        for <%= link_to answer.exercise.name, organization_course_exercise_path(answer.exercise.course.organization, answer.exercise.course, answer.exercise) %>
       <% end %>
       at <%= answer.created_at.strftime("%H:%M %d.%m.%Y") %>
     </div>
diff --git a/app/views/submissions/_form.html.erb b/app/views/submissions/_form.html.erb
index 52c7548cb..81af2e4f5 100644
--- a/app/views/submissions/_form.html.erb
+++ b/app/views/submissions/_form.html.erb
@@ -1,4 +1,4 @@
-<%= form_for(submission, :url => exercise_submissions_path(@exercise), :action => @form_action,
+<%= form_for(submission, :url => organization_course_exercise_submissions_path(@organization, @course, @exercise), :action => @form_action,
             :html => {:multipart => true, class: "form-horizontal"} ) do |f| %>
   <%= render 'shared/error_messages', :target => submission %>
 
diff --git a/app/views/submissions/_submission_details.html.erb b/app/views/submissions/_submission_details.html.erb
index 322b3f9f1..07a31d690 100644
--- a/app/views/submissions/_submission_details.html.erb
+++ b/app/views/submissions/_submission_details.html.erb
@@ -51,7 +51,7 @@
       <% end %>
 
       <% if can? :read, @exercise.solution %>
-        <li><%= link_to 'View suggested solution', exercise_solution_path(@exercise) %></li>
+        <li><%= link_to 'View suggested solution', organization_course_exercise_solution_path(@organization, @course, @exercise) %></li>
       <% end %>
 
       <% if can? :create_review, @course %>
diff --git a/config/routes.rb b/config/routes.rb
index 47adc71e9..a33379fec 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -15,7 +15,7 @@
 
     get 'course_templates', to: 'course_templates#list_for_teachers'
 
-    resources :courses do
+    resources :courses, param: :name do
       member do
         get 'refresh'
         post 'refresh'
@@ -40,10 +40,18 @@
         end
       end
 
-      resources :exercises, only: [:index] do
+      resources :exercises, param: :name, only: [:show] do
         collection do
           post 'set_disabled_statuses'
         end
+
+        member do
+          put 'submissions' => 'submissions#update_by_exercise', :as => 'update_submissions'
+        end
+
+        resources :submissions, only: [:create]
+        resource :solution, only: [:show]
+        resources :feedback_answers, only: [:index]
       end
 
       get 'help'
@@ -104,12 +112,6 @@
   get '/reset_password/:code' => 'password_reset_keys#show', :as => 'reset_password'
   delete '/reset_password/:code' => 'password_reset_keys#destroy'
 
-  resources :exercises, only: [:show] do
-    resources :submissions, only: [:create]
-    resource :solution, only: [:show]
-    resources :feedback_answers, only: [:index]
-  end
-
   resources :submissions, only: [:show, :update] do
     resource :result, only: [:create]
     resources :feedback_answers, only: [:create]
@@ -121,8 +123,6 @@
   get 'paste/:paste_key', to: 'submissions#show', as: 'paste'
   resources :reviews, only: [:update, :destroy]
 
-  put '/exercises/:exercise_id/submissions' => 'submissions#update_by_exercise', :as => 'exercise_update_submissions'
-
   resources :feedback_questions, only: [:show, :update, :destroy] do
     resource :position, only: [:update]
   end
diff --git a/lib/course_info.rb b/lib/course_info.rb
index 1c2453344..6d75e0275 100644
--- a/lib/course_info.rb
+++ b/lib/course_info.rb
@@ -59,7 +59,7 @@ def exercise_data(exercise)
     }
 
     data[:solution_zip_url] = @helpers.exercise_solution_zip_url(exercise) if @user.administrator?
-    data[:exercise_submissions_url] = @helpers.exercise_url(exercise, format: 'json', api_version: ApiVersion::API_VERSION)
+    data[:exercise_submissions_url] = @helpers.organization_course_exercise_url(exercise.course.organization, exercise.course, exercise, format: 'json', api_version: ApiVersion::API_VERSION)
     last_submission = get_latest_submission(exercise)
     data[:latest_submission_url] = @helpers.submission_url(last_submission, format: 'zip') unless last_submission.nil?
     data[:latest_submission_id] = last_submission.id unless last_submission.nil?
@@ -70,7 +70,7 @@ def exercise_data(exercise)
   private
 
   def exercise_return_url(e)
-    "#{@helpers.exercise_submissions_url(e, format: 'json')}"
+    "#{@helpers.organization_course_exercise_submissions_url(e.course.organization, e.course, e, format: 'json')}"
   end
 
   def get_latest_submission(exercise)
diff --git a/spec/controllers/assistants_controller_spec.rb b/spec/controllers/assistants_controller_spec.rb
index ae5f99139..84d9009ad 100644
--- a/spec/controllers/assistants_controller_spec.rb
+++ b/spec/controllers/assistants_controller_spec.rb
@@ -20,7 +20,7 @@
         user2 = FactoryGirl.create(:user)
         user3 = FactoryGirl.create(:user)
         @course.assistants << [user1, user2, user3]
-        get :index, organization_id: @organization.slug, course_id: @course.id
+        get :index, organization_id: @organization.slug, course_name: @course.name
         expect(assigns(:assistants)).to eq([user1, user2, user3])
       end
     end
@@ -28,20 +28,20 @@
     describe 'POST create' do
       it 'with a valid username adds a new assistant' do
         expect do
-          post :create, organization_id: @organization.slug, course_id: @course.id, username: @user.username
+          post :create, organization_id: @organization.slug, course_name: @course.name, username: @user.username
         end.to change(Assistantship, :count).by(1)
       end
 
       it 'with a invalid username doesn\'t add any assistants' do
         expect do
-          post :create, organization_id: @organization.slug, course_id: @course.id, username: 'invalid'
+          post :create, organization_id: @organization.slug, course_name: @course.name, username: 'invalid'
         end.to change(Assistantship, :count).by(0)
       end
 
       it 'with a username that already is an assistant for course, donesn\'t add' do
         Assistantship.create! user: @user, course: @course
         expect do
-          post :create, organization_id: @organization.slug, course_id: @course.id, username: @user.username
+          post :create, organization_id: @organization.slug, course_name: @course.name, username: @user.username
         end.to change(Assistantship, :count).by(0)
       end
     end
@@ -50,7 +50,7 @@
       it 'removes assistant' do
         @assistantship = Assistantship.create! user: @user, course: @course
         expect do
-          delete :destroy, organization_id: @organization.slug, course_id: @course.id, id: @assistantship.to_param
+          delete :destroy, organization_id: @organization.slug, course_name: @course.name, id: @assistantship.to_param
         end.to change(Assistantship, :count).by(-1)
       end
     end
@@ -63,14 +63,14 @@
 
     describe 'GET index' do
       it 'denies access' do
-        get :index, organization_id: @organization.slug, course_id: @course.id
+        get :index, organization_id: @organization.slug, course_name: @course.name
         expect(response.code.to_i).to eq(401)
       end
     end
 
     describe 'POST create' do
       it 'denies access' do
-        post :create, organization_id: @organization.slug, course_id: @course.id, username: @user.username
+        post :create, organization_id: @organization.slug, course_name: @course.name, username: @user.username
         expect(response.code.to_i).to eq(401)
       end
     end
@@ -78,7 +78,7 @@
     describe 'DELETE destroy' do
       it 'denies access' do
         @assistantship = Assistantship.create! user: @user, course: @course
-        delete :destroy, organization_id: @organization.slug, course_id: @course, id: @assistantship.to_param
+        delete :destroy, organization_id: @organization.slug, course_name: @course.name, id: @assistantship.to_param
         expect(response.code.to_i).to eq(401)
       end
     end
diff --git a/spec/controllers/course_notifications_controller_spec.rb b/spec/controllers/course_notifications_controller_spec.rb
index f3b6c590d..d9e86f398 100644
--- a/spec/controllers/course_notifications_controller_spec.rb
+++ b/spec/controllers/course_notifications_controller_spec.rb
@@ -16,7 +16,7 @@
         message: message
       },
       organization_id: @organization.slug,
-      course_id: @course.id
+      course_name: @course.name
     }
   end
 
diff --git a/spec/controllers/courses_controller_spec.rb b/spec/controllers/courses_controller_spec.rb
index b2da4ddda..f711a4716 100644
--- a/spec/controllers/courses_controller_spec.rb
+++ b/spec/controllers/courses_controller_spec.rb
@@ -50,7 +50,8 @@ def get_index_json(options = {})
 
   describe 'GET show' do
     before :each do
-      @course = FactoryGirl.create(:course)
+      @course = FactoryGirl.create(:course, organization: @organization)
+      @exercise = FactoryGirl.create(:exercise, course: @course)
     end
 
     describe 'for administrators' do
@@ -61,10 +62,10 @@ def get_index_json(options = {})
       it "should show everyone's submissions" do
         user1 = FactoryGirl.create(:user)
         user2 = FactoryGirl.create(:user)
-        sub1 = FactoryGirl.create(:submission, user: user1, course: @course)
-        sub2 = FactoryGirl.create(:submission, user: user2, course: @course)
+        sub1 = FactoryGirl.create(:submission, user: user1, course: @course, exercise: @exercise)
+        sub2 = FactoryGirl.create(:submission, user: user2, course: @course, exercise: @exercise)
 
-        get :show, organization_id: @organization.slug, id: @course.id
+        get :show, organization_id: @organization.slug, name: @course.name
 
         expect(assigns['submissions']).to include(sub1)
         expect(assigns['submissions']).to include(sub2)
@@ -80,7 +81,7 @@ def get_index_json(options = {})
         FactoryGirl.create(:submission, course: @course)
         FactoryGirl.create(:submission, course: @course)
 
-        get :show, organization_id: @organization.slug, id: @course.id
+        get :show, organization_id: @organization.slug, name: @course.name
 
         expect(assigns['submissions']).to be_nil
       end
@@ -95,7 +96,7 @@ def get_index_json(options = {})
         my_sub = FactoryGirl.create(:submission, user: @user, course: @course)
         other_guys_sub = FactoryGirl.create(:submission, user: other_user, course: @course)
 
-        get :show, organization_id: @organization.slug, id: @course.id
+        get :show, organization_id: @organization.slug, name: @course.name
 
         expect(assigns['submissions']).to include(my_sub)
         expect(assigns['submissions']).not_to include(other_guys_sub)
@@ -104,7 +105,7 @@ def get_index_json(options = {})
 
     describe 'in JSON format' do
       before :each do
-        @course = FactoryGirl.create(:course, name: 'Course1')
+        @course = FactoryGirl.create(:course, name: 'Course1', organization: @organization)
         @course.exercises << FactoryGirl.create(:returnable_exercise, name: 'Exercise1', course: @course)
         @course.exercises << FactoryGirl.create(:returnable_exercise, name: 'Exercise2', course: @course)
         @course.exercises << FactoryGirl.create(:returnable_exercise, name: 'Exercise3', course: @course)
@@ -114,7 +115,7 @@ def get_show_json(options = {}, parse_json = true)
         options = {
           format: 'json',
           api_version: ApiVersion::API_VERSION,
-          id: @course.id.to_s,
+          name: @course.name,
           organization_id: @organization.slug
         }.merge options
         @request.env['HTTP_AUTHORIZATION'] = ActionController::HttpAuthentication::Basic.encode_credentials(@user.login, @user.password)
@@ -129,11 +130,13 @@ def get_show_json(options = {}, parse_json = true)
       it 'should render the exercises for each course' do
         result = get_show_json
 
+        ex = @course.exercises[0];
+
         exs = result['course']['exercises']
         expect(exs[0]['name']).to eq('Exercise1')
         expect(exs[1]['name']).to eq('Exercise2')
-        expect(exs[0]['zip_url']).to eq(exercise_url(@course.exercises[0].id, format: 'zip'))
-        expect(exs[0]['return_url']).to eq(exercise_submissions_url(@course.exercises[0].id, format: 'json'))
+        expect(exs[0]['zip_url']).to eq(organization_course_exercise_url(ex.course.organization, ex.course, ex, format: 'zip'))
+        expect(exs[0]['return_url']).to eq(organization_course_exercise_submissions_url(ex.course.organization, ex.course, ex, format: 'json'))
       end
 
       it 'should include only visible exercises' do
@@ -281,7 +284,7 @@ def get_show_json(options = {}, parse_json = true)
 
     it 'can\'t refresh if course created from template' do
       @course = FactoryGirl.create :course, organization: @organization, course_template: @template, source_url: @template.source_url
-      post :refresh, organization_id: @organization.slug, id: @course.id
+      post :refresh, organization_id: @organization.slug, name: @course.name
       expect(response.code.to_i).to eq(401)
     end
   end
@@ -303,7 +306,7 @@ def get_show_json(options = {}, parse_json = true)
     describe 'with valid parameters' do
       before :each do
         Teachership.create user: @user, organization: @organization
-        put :update, organization_id: @organization.to_param, id: @course.to_param, course: {
+        put :update, organization_id: @organization.to_param, name: @course.to_param, course: {
                        title: 'newTitle',
                        description: 'newDescription',
                        material_url: 'http://newMaterial.com',
@@ -327,21 +330,21 @@ def get_show_json(options = {}, parse_json = true)
     describe 'with invalid parameters' do
       it 're-renders course update form' do
         Teachership.create user: @user, organization: @organization
-        put :update, organization_id: @organization.to_param, id: @course.to_param, course: {title: 'a' * 41}
+        put :update, organization_id: @organization.to_param, name: @course.to_param, course: {title: 'a' * 41}
         expect(response).to render_template('edit')
       end
     end
 
     it 'can\'t update course name' do
       Teachership.create user: @user, organization: @organization
-      put :update, organization_id: @organization.to_param, id: @course.to_param, course: {name: 'newName'}
+      put :update, organization_id: @organization.to_param, name: @course.to_param, course: {name: 'newName'}
       expect(Course.last.name).to eq('oldName')
     end
 
     it 'can\'t update course template id' do
       Teachership.create user: @user, organization: @organization
       old_id = @course.course_template_id
-      put :update, organization_id: @organization.to_param, id: @course.to_param, course: {course_template_id: 2}
+      put :update, organization_id: @organization.to_param, name: @course.to_param, course: {course_template_id: 2}
       expect(Course.last.course_template_id).to eq(old_id)
     end
 
@@ -355,19 +358,19 @@ def get_show_json(options = {}, parse_json = true)
       end
 
       it 'can\'t update source_url' do
-        put :update, organization_id: @organization.to_param, id: @course.to_param, course: {source_url: @new_repo_path}
+        put :update, organization_id: @organization.to_param, name: @course.to_param, course: {source_url: @new_repo_path}
         expect(Course.last.source_url).to eq(@template.source_url)
       end
 
       it 'can\'t update git_branch' do
-        put :update, organization_id: @organization.to_param, id: @course.to_param, course: {git_branch: 'ufobranch'}
+        put :update, organization_id: @organization.to_param, name: @course.to_param, course: {git_branch: 'ufobranch'}
         expect(Course.last.git_branch).to eq('master')
       end
     end
 
     describe 'when non-teacher attemps to update' do
       before :each do
-        put :update, organization_id: @organization.to_param, id: @course.to_param, course: {title: 'newTitle', description: 'newDescription', material_url: 'http://newMaterial.com'}
+        put :update, organization_id: @organization.to_param, name: @course.to_param, course: {title: 'newTitle', description: 'newDescription', material_url: 'http://newMaterial.com'}
       end
 
       it 'should respond with 401' do
@@ -385,13 +388,13 @@ def get_show_json(options = {}, parse_json = true)
 
   describe 'POST disable' do
     before :each do
-      @course = FactoryGirl.create(:course)
+      @course = FactoryGirl.create(:course, organization: @organization)
     end
 
     describe 'As a teacher' do
       it 'disables the course' do
         controller.current_user = @teacher
-        post :disable, organization_id: @organization.slug, id: @course.id.to_s
+        post :disable, organization_id: @organization.slug, name: @course.name
         expect(Course.find(@course.id).disabled?).to eq(true)
       end
     end
@@ -399,7 +402,7 @@ def get_show_json(options = {}, parse_json = true)
     describe 'As a student' do
       it 'denies access' do
         controller.current_user = @user
-        post :disable, organization_id: @organization.slug, id: @course.id.to_s
+        post :disable, organization_id: @organization.slug, name: @course.name
         expect(response.code.to_i).to eq(401)
       end
     end
@@ -407,13 +410,13 @@ def get_show_json(options = {}, parse_json = true)
 
   describe 'POST enable' do
     before :each do
-      @course = FactoryGirl.create(:course)
+      @course = FactoryGirl.create(:course, organization: @organization)
     end
 
     describe 'As a teacher' do
       it 'enables the course' do
         controller.current_user = @teacher
-        post :enable, organization_id: @organization.slug, id: @course.id.to_s
+        post :enable, organization_id: @organization.slug, name: @course.name
         expect(Course.find(@course.id).disabled?).to eq(false)
       end
     end
@@ -421,7 +424,7 @@ def get_show_json(options = {}, parse_json = true)
     describe 'As a student' do
       it 'denies access' do
         controller.current_user = @user
-        post :disable, organization_id: @organization.slug, id: @course.id.to_s
+        post :disable, organization_id: @organization.slug, name: @course.name
         expect(response.code.to_i).to eq(401)
       end
     end
@@ -441,7 +444,7 @@ def get_show_json(options = {}, parse_json = true)
 
       post :save_deadlines,
            organization_id: @organization.slug,
-           id: @course.id,
+           name: @course.name,
            empty_group: {
                soft: { static: '1.1.2000', unlock: '' },
                hard: { static: '', unlock: 'unlock + 2 weeks' }
@@ -464,7 +467,7 @@ def get_show_json(options = {}, parse_json = true)
 
       post :save_deadlines,
            organization_id: @organization.slug,
-           id: @course.id,
+           name: @course.name,
            group: {
                group1: {
                    soft: { static: '1.1.2000', unlock: 'unlock + 7 days' },
@@ -494,10 +497,9 @@ def get_show_json(options = {}, parse_json = true)
 
   describe 'GET manage_unlocks' do
     it 'when non-teacher should respond with a 401' do
-      @course = FactoryGirl.create :course
-      @course.organization = @organization
+      @course = FactoryGirl.create :course, organization: @organization
       controller.current_user = @user
-      get :manage_unlocks, organization_id: @organization.slug, id: @course.id
+      get :manage_unlocks, organization_id: @organization.slug, name: @course.name
       expect(response.code.to_i).to eq(401)
     end
   end
@@ -518,7 +520,7 @@ def get_show_json(options = {}, parse_json = true)
         @course.exercises.create(name: 'e2')
         @course.exercises.create(name: 'e3')
 
-        post :save_unlocks, organization_id: @organization.slug, id: @course.id, empty_group: { '0' => '1.2.2000' }
+        post :save_unlocks, organization_id: @organization.slug, name: @course.name, empty_group: { '0' => '1.2.2000' }
 
         @course.exercise_group_by_name('').exercises(false).each do |e|
           expect(e.unlock_spec_obj.valid_after).to be_within(1.day).of Time.new(2000, 2, 1)
@@ -531,7 +533,7 @@ def get_show_json(options = {}, parse_json = true)
         @course.exercises.create(name: 'group1-e3')
         @course.exercises.create(name: 'group2-e1')
 
-        post :save_unlocks, organization_id: @organization.slug, id: @course.id, group: { group1: { '0' => '1.2.2000' } }
+        post :save_unlocks, organization_id: @organization.slug, name: @course.name, group: { group1: { '0' => '1.2.2000' } }
 
         @course.exercise_group_by_name('group1').exercises(false).each do |e|
           expect(e.unlock_spec_obj.valid_after).to be_within(1.day).of Time.new(2000, 2, 1)
@@ -546,8 +548,8 @@ def get_show_json(options = {}, parse_json = true)
         @course.exercises.create(name: 'e2')
         @course.exercises.create(name: 'e3')
 
-        post :save_unlocks, organization_id: @organization.slug, id: @course.id, empty_group: { 0 => '1.2.2000' }
-        post :save_unlocks, organization_id: @organization.slug, id: @course.id, empty_group: { 0 => '' }
+        post :save_unlocks, organization_id: @organization.slug, name: @course.name, empty_group: { 0 => '1.2.2000' }
+        post :save_unlocks, organization_id: @organization.slug, name: @course.name, empty_group: { 0 => '' }
 
         @course.exercise_group_by_name('').exercises(false).each do |e|
           expect(e.unlock_spec_obj.valid_after).to be_nil
@@ -559,7 +561,7 @@ def get_show_json(options = {}, parse_json = true)
         @course.exercises.create(name: 'e2')
         @course.exercises.create(name: 'e3')
 
-        post :save_unlocks, organization_id: @organization.slug, id: @course.id,
+        post :save_unlocks, organization_id: @organization.slug, name: @course.name,
              empty_group: { '0' => '1.2.2000', '1' => 'exercise e1', '2' => '5% of e2' }
 
         @course.exercise_group_by_name('').exercises(false).each do |e|
@@ -573,7 +575,7 @@ def get_show_json(options = {}, parse_json = true)
 
     it 'when non-teacher should respond with a 401' do
       @course.exercises.create(name: 'e')
-      post :save_unlocks, organization_id: @organization.slug, id: @course.id, empty_group: { 0 => '1.2.2000' }
+      post :save_unlocks, organization_id: @organization.slug, name: @course.name, empty_group: { 0 => '1.2.2000' }
       expect(response.code.to_i).to eq(401)
     end
   end
@@ -586,7 +588,7 @@ def get_show_json(options = {}, parse_json = true)
     describe 'when teacher' do
       it 'toggles visibility of submsission results' do
         controller.current_user = @teacher
-        post :toggle_submission_result_visibility, organization_id: @organization.slug, id: @course.id
+        post :toggle_submission_result_visibility, organization_id: @organization.slug, name: @course.name
         @course.reload
         expect(@course.hide_submission_results).to be true
         expect(response).to redirect_to(organization_course_path)
@@ -597,7 +599,7 @@ def get_show_json(options = {}, parse_json = true)
       it 'toggles visibility of submsission results' do
         Assistantship.create(user: @user, course: @course)
         controller.current_user = @user
-        post :toggle_submission_result_visibility, organization_id: @organization.slug, id: @course.id
+        post :toggle_submission_result_visibility, organization_id: @organization.slug, name: @course.name
         @course.reload
         expect(@course.hide_submission_results).to be true
         expect(response).to redirect_to(organization_course_path)
@@ -607,7 +609,7 @@ def get_show_json(options = {}, parse_json = true)
     describe 'when non-teacher or non-admin' do
       it 'acces denied' do
         controller.current_user = @user
-        post :toggle_submission_result_visibility, organization_id: @organization.slug, id: @course.id
+        post :toggle_submission_result_visibility, organization_id: @organization.slug, name: @course.name
         @course.reload
         expect(response.code.to_i).to eq(401)
       end
diff --git a/spec/controllers/emails_controller_spec.rb b/spec/controllers/emails_controller_spec.rb
index 8a9f34bd2..c111c955c 100644
--- a/spec/controllers/emails_controller_spec.rb
+++ b/spec/controllers/emails_controller_spec.rb
@@ -47,7 +47,7 @@
 
       it 'assigns users in @students array if they have submitted exercises to the course if current user is teacher' do
         controller.current_user = @teacher
-        get :index, organization_id: @organization.slug, id: @course.id
+        get :index, organization_id: @organization.slug, name: @course.name
         expect(assigns(:students)).to include(@user1)
         expect(assigns(:students)).to include(@user2)
         expect(assigns(:students)).to_not include(@user3)
@@ -55,7 +55,7 @@
 
       it 'denies access for non-teachers' do
         controller.current_user = @user
-        get :index, organization_id: @organization.slug, id: @course.id
+        get :index, organization_id: @organization.slug, name: @course.name
         expect(response.code.to_i).to eq(401)
       end
     end
diff --git a/spec/controllers/exercise_status_controller_spec.rb b/spec/controllers/exercise_status_controller_spec.rb
index 97c083589..eb5a55312 100644
--- a/spec/controllers/exercise_status_controller_spec.rb
+++ b/spec/controllers/exercise_status_controller_spec.rb
@@ -3,8 +3,7 @@
 describe ExerciseStatusController, type: :controller do
   before :each do
     @organization = FactoryGirl.create(:accepted_organization)
-    @course = FactoryGirl.create(:course)
-    @course.organization = @organization
+    @course = FactoryGirl.create(:course, organization: @organization)
     @exercise = FactoryGirl.create(:exercise, course: @course)
     @exercise2 = FactoryGirl.create(:exercise, course: @course)
     @exercise3 = FactoryGirl.create(:exercise, course: @course)
@@ -40,7 +39,7 @@
       end
 
       def do_get
-        get :show, organization_id: @organization.slug, course_id: @course.id, id: @user.id, format: :json, api_version: ApiVersion::API_VERSION
+        get :show, organization_id: @organization.slug, course_name: @course.name, id: @user.id, format: :json, api_version: ApiVersion::API_VERSION
       end
 
       it 'should show completition status for submitted exercises' do
diff --git a/spec/controllers/exercises_controller_spec.rb b/spec/controllers/exercises_controller_spec.rb
index ec89d4155..1ef034dca 100644
--- a/spec/controllers/exercises_controller_spec.rb
+++ b/spec/controllers/exercises_controller_spec.rb
@@ -4,13 +4,12 @@
   describe 'GET show' do
     before :each do
       @organization = FactoryGirl.create(:accepted_organization)
-      @course = FactoryGirl.create(:course)
-      @course.organization = @organization
+      @course = FactoryGirl.create(:course, organization: @organization)
     end
     let!(:exercise) { FactoryGirl.create(:exercise, course: @course) }
 
     def get_show
-      get :show, organization_id: @organization.slug, id: exercise.id
+      get :show, organization_id: @organization.slug, course_name: @course.name, name: exercise.name
     end
 
     describe 'for guests' do
@@ -69,7 +68,7 @@ def get_show
     end
 
     def post_set_disabled_statuses(options = {})
-      post :set_disabled_statuses, options.merge(organization_id: @organization.slug, course_id: @course.id)
+      post :set_disabled_statuses, options.merge(organization_id: @organization.slug, course_name: @course.name)
     end
 
     describe 'as a teacher' do
diff --git a/spec/controllers/points_controller_spec.rb b/spec/controllers/points_controller_spec.rb
index 112e34dc3..6450132ae 100644
--- a/spec/controllers/points_controller_spec.rb
+++ b/spec/controllers/points_controller_spec.rb
@@ -7,7 +7,7 @@
   before :each do
     @user = FactoryGirl.create(:user)
     @organization = FactoryGirl.create(:accepted_organization)
-    @course = FactoryGirl.create :course, organization: @organization
+    @course = FactoryGirl.create(:course, organization: @organization)
     @sheetname = 'testsheet'
     @exercise = FactoryGirl.create(:exercise, course: @course, gdocs_sheet: @sheetname)
     @submission = FactoryGirl.create(:submission,
@@ -26,14 +26,14 @@
   describe 'GET index' do
     describe 'when user has participated in a course' do
       it 'should show a page' do
-        get :index, organization_id: @organization.slug, course_id: @course.id
+        get :index, organization_id: @organization.slug, course_name: @course.name
         expect(response).to be_success
       end
 
       it 'should not show a page when submission result are hidden' do
         @course.hide_submission_results = true
         @course.save!
-        get :index, organization_id: @organization.slug, course_id: @course.id
+        get :index, organization_id: @organization.slug, course_name: @course.name
         expect(response.code.to_i).to eq(401)
       end
     end
@@ -43,29 +43,29 @@
     describe 'when user has participated in a course' do
       it 'should show a page' do
         get :show, organization_id: @organization.slug,
-            course_id: @course.id, id: @sheetname
+            course_name: @course.name, id: @sheetname
         expect(response).to be_success
       end
 
       it 'should contain @user login' do
-        get :show, organization_id: @organization.slug, course_id: @course.id, id: @sheetname
+        get :show, organization_id: @organization.slug, course_name: @course.name, id: @sheetname
         expect(response.body).to have_content(@user.login)
       end
 
       it 'should contain available point name' do
-        get :show, organization_id: @organization.slug, course_id: @course.id, id: @sheetname
+        get :show, organization_id: @organization.slug, course_name: @course.name, id: @sheetname
         expect(response.body).to have_content(@available_point.name)
       end
 
       it 'should contain a success marker' do
-        get :show, organization_id: @organization.slug, course_id: @course.id, id: @sheetname
+        get :show, organization_id: @organization.slug, course_name: @course.name, id: @sheetname
         expect(response.body).to have_content('✔')
       end
 
       it 'should not show a page when submission result are hidden' do
         @course.hide_submission_results = true
         @course.save!
-        get :show, organization_id: @organization.slug, course_id: @course.id, id: @sheetname
+        get :show, organization_id: @organization.slug, course_name: @course.name, id: @sheetname
         expect(response.code.to_i).to eq(401)
       end
     end
diff --git a/spec/features/teacher_adds_assistants_to_course_spec.rb b/spec/features/teacher_adds_assistants_to_course_spec.rb
index eb4e0e5a5..c7fe43492 100644
--- a/spec/features/teacher_adds_assistants_to_course_spec.rb
+++ b/spec/features/teacher_adds_assistants_to_course_spec.rb
@@ -49,7 +49,7 @@
 
     log_out
     log_in_as(@assistant.username, 'newfoobar')
-    visit "/org/slug/courses/#{@course.id}"
+    visit "/org/slug/courses/#{@course.name}"
     click_link 'Manage deadlines'
     fill_in 'empty_group_hard_static', with: '1.1.2000'
     click_button 'Save changes'
@@ -57,7 +57,7 @@
     expect(page).to have_content('Successfully saved deadlines.')
     expect(page).to have_field('empty_group_hard_static', with: '1.1.2000')
 
-    visit "/org/slug/courses/#{@course.id}"
+    visit "/org/slug/courses/#{@course.name}"
     click_link 'Manage unlock conditions'
 
     fill_in 'empty_group_0', with: '4.6.2015'
@@ -74,7 +74,7 @@
 
     log_out
     log_in_as(@assistant.username, 'newfoobar')
-    visit "/org/slug/courses/#{course2.id}"
+    visit "/org/slug/courses/#{course2.name}"
     expect(page).not_to have_content('Manage deadlines')
     expect(page).not_to have_content('Manage unlock conditions')
   end
diff --git a/spec/features/teacher_disables_exercises_spec.rb b/spec/features/teacher_disables_exercises_spec.rb
index 853008f1f..a30e51367 100644
--- a/spec/features/teacher_disables_exercises_spec.rb
+++ b/spec/features/teacher_disables_exercises_spec.rb
@@ -89,12 +89,12 @@
 
     log_in_as(@user.login, @user.password)
 
-    visit "/exercises/#{@ex1.id}"
+    visit "/org/slug/courses/#{@course.name}/exercises/#{@ex1.name}"
 
     expect(page).to have_content('Access denied')
   end
 
   def visit_course(course)
-    visit "/org/slug/courses/#{course.id}"
+    visit "/org/slug/courses/#{course.name}"
   end
 end
diff --git a/spec/features/teacher_edits_unlock_dates_spec.rb b/spec/features/teacher_edits_unlock_dates_spec.rb
index ed4e23b94..71db7c3c9 100644
--- a/spec/features/teacher_edits_unlock_dates_spec.rb
+++ b/spec/features/teacher_edits_unlock_dates_spec.rb
@@ -24,7 +24,7 @@
   end
 
   def visit_course
-    visit "/org/slug/courses/#{@course.id}"
+    visit "/org/slug/courses/#{@course.name}"
   end
 
   scenario 'Teacher sees default unlock dates' do
diff --git a/spec/features/teacher_has_admin_abilities_to_own_course_spec.rb b/spec/features/teacher_has_admin_abilities_to_own_course_spec.rb
index 08e984e59..d2be4bcae 100644
--- a/spec/features/teacher_has_admin_abilities_to_own_course_spec.rb
+++ b/spec/features/teacher_has_admin_abilities_to_own_course_spec.rb
@@ -28,8 +28,12 @@
     log_in_as(@teacher.login, 'xooxer')
   end
 
+  def visit_course
+    visit "/org/slug/courses/#{@course.name}"
+  end
+
   scenario 'Teacher can see model solution for exercise' do
-    visit '/exercises/1'
+    visit "/org/slug/courses/#{@course.name}/exercises/#{@exercise1.name}"
     expect(page).to have_content('View suggested solution')
 
     click_link 'View suggested solution'
@@ -39,7 +43,7 @@
   end
 
   scenario 'Teacher can see all submissions for his organizations courses' do
-    visit '/org/slug/courses/1'
+    visit_course
 
     expect(page).to have_content('Latest submissions')
     expect(page).not_to have_content('No data available in table')
@@ -56,7 +60,7 @@
   scenario 'Teacher can see users points from his own courses' do
     available_point = FactoryGirl.create :available_point, exercise: @exercise1
     available_point.award_to(@student, @submission)
-    visit '/org/slug/courses/1'
+    visit_course
     click_link 'View points'
 
     expect(page).to have_content('1/6')
@@ -64,7 +68,7 @@
   end
 
   scenario 'Teacher can make code review' do
-    visit '/org/slug/courses/1'
+    visit_course
 
     expect(page).to have_content('1 code review requested')
     click_link '1 code review requested'
@@ -77,7 +81,7 @@
   end
 
   scenario 'Teacher can manage course feedback questions' do
-    visit '/org/slug/courses/1'
+    visit_course
     click_link 'Manage feedback questions'
     click_link 'Add question'
 
@@ -104,7 +108,7 @@
     question = FactoryGirl.create :feedback_question, course: @course, question: 'Meaning of life?'
     answer = FactoryGirl.create :feedback_answer, feedback_question: question, course: @course, exercise: @exercise1, submission: @submission, answer: 'no idea'
 
-    visit '/org/slug/courses/1'
+    visit_course
     click_link 'View feedback'
 
     expect(page).not_to have_content('access denied')
diff --git a/spec/features/teacher_hides_submission_results_spec.rb b/spec/features/teacher_hides_submission_results_spec.rb
index 9d1da3a1c..54fb75200 100644
--- a/spec/features/teacher_hides_submission_results_spec.rb
+++ b/spec/features/teacher_hides_submission_results_spec.rb
@@ -28,7 +28,7 @@
   end
 
   def visit_course
-    visit "/org/#{@organization.slug}/courses/#{@course.id}"
+    visit "/org/#{@organization.slug}/courses/#{@course.name}"
   end
 
   scenario "Teacher can see button 'Unhide submisson results' when result are hidden" do
diff --git a/spec/features/teacher_sets_deadlines_spec.rb b/spec/features/teacher_sets_deadlines_spec.rb
index cc3e919de..f7cc97380 100644
--- a/spec/features/teacher_sets_deadlines_spec.rb
+++ b/spec/features/teacher_sets_deadlines_spec.rb
@@ -29,7 +29,7 @@
   end
 
   def visit_course
-    visit "/org/slug/courses/#{@course.id}"
+    visit "/org/slug/courses/#{@course.name}"
   end
 
   scenario 'Teacher succeeds at setting deadlines' do
diff --git a/spec/features/teacher_show_course_json_spec.rb b/spec/features/teacher_show_course_json_spec.rb
index e3701f5a0..f967aca35 100644
--- a/spec/features/teacher_show_course_json_spec.rb
+++ b/spec/features/teacher_show_course_json_spec.rb
@@ -17,7 +17,7 @@
   end
 
   scenario 'Page returns organizations courses as json' do
-    visit "/org/slug/courses/#{@course.id}/courses.json?api_version=7"
+    visit "/org/slug/courses/#{@course.name}/courses.json?api_version=7"
 
     expect(page).to have_content('course_1')
     expect(page).not_to have_content('course_2')