diff --git a/src/NSwag.AspNet.Owin/Middlewares/SwaggerUiIndexMiddleware.cs b/src/NSwag.AspNet.Owin/Middlewares/SwaggerUiIndexMiddleware.cs
index 6dfaa50c64..7ac6f233c9 100644
--- a/src/NSwag.AspNet.Owin/Middlewares/SwaggerUiIndexMiddleware.cs
+++ b/src/NSwag.AspNet.Owin/Middlewares/SwaggerUiIndexMiddleware.cs
@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Owin;
 using NSwag.Generation;
@@ -30,7 +31,7 @@ public override async Task Invoke(IOwinContext context)
                 {
                     context.Response.Headers["Content-Type"] = "text/html; charset=utf-8";
                     context.Response.StatusCode = 200;
-                    context.Response.Write(_settings.TransformHtml(reader.ReadToEnd(), context.Request));
+                    context.Response.Write(await _settings.TransformHtmlAsync(reader.ReadToEnd(), context.Request, CancellationToken.None));
                 }
             }
             else
diff --git a/src/NSwag.AspNetCore/ApiverseUiSettings.cs b/src/NSwag.AspNetCore/ApiverseUiSettings.cs
index ec546dc26b..548efafbeb 100644
--- a/src/NSwag.AspNetCore/ApiverseUiSettings.cs
+++ b/src/NSwag.AspNetCore/ApiverseUiSettings.cs
@@ -7,6 +7,8 @@
 //-----------------------------------------------------------------------
 
 using Microsoft.AspNetCore.Http;
+using System.Threading;
+using System.Threading.Tasks;
 
 namespace NSwag.AspNetCore
 {
@@ -31,9 +33,9 @@ public ApimundoUiSettings()
         /// </summary>
         public string ApimundoUrl { get; set; } = "https://apimundo.com";
 
-        internal override string TransformHtml(string html, HttpRequest request)
+        internal override Task<string> TransformHtmlAsync(string html, HttpRequest request, CancellationToken cancellationToken)
         {
-            return html;
+            return Task.FromResult(html);
         }
     }
 }
diff --git a/src/NSwag.AspNetCore/Middlewares/SwaggerUiIndexMiddleware.cs b/src/NSwag.AspNetCore/Middlewares/SwaggerUiIndexMiddleware.cs
index 6a2fc82d6f..2889168a43 100644
--- a/src/NSwag.AspNetCore/Middlewares/SwaggerUiIndexMiddleware.cs
+++ b/src/NSwag.AspNetCore/Middlewares/SwaggerUiIndexMiddleware.cs
@@ -30,7 +30,11 @@ public async Task Invoke(HttpContext context)
                 {
                     context.Response.Headers["Content-Type"] = "text/html; charset=utf-8";
                     context.Response.StatusCode = 200;
-                    await context.Response.WriteAsync(_settings.TransformHtml(await reader.ReadToEndAsync(), context.Request));
+                    await context.Response.WriteAsync(
+                        await _settings.TransformHtmlAsync(
+                            await reader.ReadToEndAsync(), 
+                            context.Request, 
+                            context.RequestAborted));
                 }
             }
             else
diff --git a/src/NSwag.AspNetCore/ReDocSettings.cs b/src/NSwag.AspNetCore/ReDocSettings.cs
index fad349d2ed..938be6e972 100644
--- a/src/NSwag.AspNetCore/ReDocSettings.cs
+++ b/src/NSwag.AspNetCore/ReDocSettings.cs
@@ -8,6 +8,8 @@
 
 using NSwag.Generation;
 using System.Collections.Generic;
+using System.Threading.Tasks;
+using System.Threading;
 #if AspNetOwin
 using Microsoft.Owin;
 
@@ -30,15 +32,15 @@ public class ReDocSettings : SwaggerUiSettingsBase
         public IDictionary<string, object> AdditionalSettings { get; } = new Dictionary<string, object>();
 
 #if AspNetOwin
-        internal override string TransformHtml(string html, IOwinRequest request)
+        internal override Task<string> TransformHtmlAsync(string html, IOwinRequest request, CancellationToken cancellationToken)
 #else
-        internal override string TransformHtml(string html, HttpRequest request)
+        internal override Task<string> TransformHtmlAsync(string html, HttpRequest request, CancellationToken cancellationToken)
 #endif
         {
             html = html.Replace("{AdditionalSettings}", GenerateAdditionalSettings(AdditionalSettings));
             html = html.Replace("{CustomStyle}", GetCustomStyleHtml(request));
             html = html.Replace("{CustomScript}", GetCustomScriptHtml(request));
-            return html;
+            return Task.FromResult(html);
         }
     }
 }
\ No newline at end of file
diff --git a/src/NSwag.AspNetCore/SwaggerUi3Settings.cs b/src/NSwag.AspNetCore/SwaggerUi3Settings.cs
index 88099b0ff4..6855bf969b 100644
--- a/src/NSwag.AspNetCore/SwaggerUi3Settings.cs
+++ b/src/NSwag.AspNetCore/SwaggerUi3Settings.cs
@@ -15,6 +15,8 @@
 using Newtonsoft.Json;
 using NSwag.Generation;
 using NJsonSchema;
+using System.Threading;
+using System.Threading.Tasks;
 
 #if AspNetOwin
 using Microsoft.Owin;
@@ -121,12 +123,19 @@ public bool WithCredentials
         /// <summary>Gets or sets the Swagger URL routes (must start with '/', hides SwaggerRoute).</summary>
         public ICollection<SwaggerUi3Route> SwaggerRoutes { get; } = new List<SwaggerUi3Route>();
 
+        /// <summary>Gets or sets the Swagger URL routes factory (SwaggerRoutes is ignored when set).</summary>
+#if AspNetOwin
+        public Func<IOwinRequest, CancellationToken, Task<IEnumerable<SwaggerUi3Route>>> SwaggerRoutesFactory { get; set; }
+#else
+        public Func<HttpRequest, CancellationToken, Task<IEnumerable<SwaggerUi3Route>>> SwaggerRoutesFactory { get; set; }
+#endif
+
         internal override string ActualSwaggerDocumentPath => SwaggerRoutes.Any() ? "" : base.ActualSwaggerDocumentPath;
 
 #if AspNetOwin
-        internal override string TransformHtml(string html, IOwinRequest request)
+        internal override async Task<string> TransformHtmlAsync(string html, IOwinRequest request, CancellationToken cancellationToken)
 #else
-        internal override string TransformHtml(string html, HttpRequest request)
+        internal override async Task<string> TransformHtmlAsync(string html, HttpRequest request, CancellationToken cancellationToken)
 #endif
         {
             var htmlBuilder = new StringBuilder(html);
@@ -148,11 +157,15 @@ internal override string TransformHtml(string html, HttpRequest request)
                 }
             }
 
-            htmlBuilder.Replace("{Urls}", !SwaggerRoutes.Any()
+            var swaggerRoutes = SwaggerRoutesFactory != null ? 
+                (await SwaggerRoutesFactory(request, cancellationToken)).ToList() : 
+                SwaggerRoutes;
+
+            htmlBuilder.Replace("{Urls}", !swaggerRoutes.Any()
                 ? "undefined"
                 : JsonConvert.SerializeObject(
 #pragma warning disable 618
-                    SwaggerRoutes.Select(r => new SwaggerUi3Route(r.Name,
+                    swaggerRoutes.Select(r => new SwaggerUi3Route(r.Name,
                         TransformToExternalPath(r.Url.Substring(MiddlewareBasePath?.Length ?? 0), request)))
 #pragma warning restore 618
                 ));
diff --git a/src/NSwag.AspNetCore/SwaggerUiSettings.cs b/src/NSwag.AspNetCore/SwaggerUiSettings.cs
index deef42c06f..430b82efb9 100644
--- a/src/NSwag.AspNetCore/SwaggerUiSettings.cs
+++ b/src/NSwag.AspNetCore/SwaggerUiSettings.cs
@@ -11,6 +11,8 @@
 using System.Text;
 using Newtonsoft.Json;
 using NSwag.Generation;
+using System.Threading.Tasks;
+using System.Threading;
 
 #if AspNetOwin
 using Microsoft.Owin;
@@ -52,9 +54,9 @@ public class SwaggerUiSettings : SwaggerUiSettingsBase
         public bool ShowRequestHeaders { get; set; } = false;
 
 #if AspNetOwin
-        internal override string TransformHtml(string html, IOwinRequest request)
+        internal override Task<string> TransformHtmlAsync(string html, IOwinRequest request, CancellationToken cancellationToken)
 #else
-        internal override string TransformHtml(string html, HttpRequest request)
+        internal override Task<string> TransformHtmlAsync(string html, HttpRequest request, CancellationToken cancellationToken)
 #endif
         {
             var htmlBuilder = new StringBuilder(html);
@@ -74,7 +76,7 @@ internal override string TransformHtml(string html, HttpRequest request)
                 .Replace("{CustomStyle}", GetCustomStyleHtml(request))
                 .Replace("{CustomScript}", GetCustomScriptHtml(request));
 
-            return htmlBuilder.ToString();
+            return Task.FromResult(htmlBuilder.ToString());
         }
     }
 }
\ No newline at end of file
diff --git a/src/NSwag.AspNetCore/SwaggerUiSettingsBase.cs b/src/NSwag.AspNetCore/SwaggerUiSettingsBase.cs
index 1f058dcb37..ee5df125bd 100644
--- a/src/NSwag.AspNetCore/SwaggerUiSettingsBase.cs
+++ b/src/NSwag.AspNetCore/SwaggerUiSettingsBase.cs
@@ -14,6 +14,8 @@
 using Newtonsoft.Json;
 using System.Linq;
 using System.Text;
+using System.Threading.Tasks;
+using System.Threading;
 #if AspNetOwin
 using Microsoft.Owin;
 
@@ -62,11 +64,11 @@ public SwaggerUiSettingsBase()
 #if AspNetOwin
         public Func<string, IOwinRequest, string> TransformToExternalPath { get; set; }
 
-        internal abstract string TransformHtml(string html, IOwinRequest request);
+        internal abstract Task<string> TransformHtmlAsync(string html, IOwinRequest request, CancellationToken cancellationToken);
 #else
         public Func<string, HttpRequest, string> TransformToExternalPath { get; set; }
 
-        internal abstract string TransformHtml(string html, HttpRequest request);
+        internal abstract Task<string> TransformHtmlAsync(string html, HttpRequest request, CancellationToken cancellationToken);
 #endif
 
         /// <summary>