diff --git a/CheckerApi/Jobs/ForkWatchJob.cs b/CheckerApi/Jobs/ForkWatchJob.cs
new file mode 100644
index 0000000..a0bb47c
--- /dev/null
+++ b/CheckerApi/Jobs/ForkWatchJob.cs
@@ -0,0 +1,211 @@
+using AutoMapper;
+using CheckerApi.Extensions;
+using CheckerApi.Models;
+using CheckerApi.Models.Config;
+using CheckerApi.Models.DTO;
+using CheckerApi.Models.Rpc;
+using CheckerApi.Services.Interfaces;
+using CheckerApi.Utils;
+using Microsoft.Extensions.Caching.Memory;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using Quartz;
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+
+namespace CheckerApi.Jobs
+{
+    [DisallowConcurrentExecution]
+    public class ForkWatchJob : Job
+    {
+        public override void Execute(JobDataMap data, IServiceProvider serviceProvider)
+        {
+            var executor = new WatchJobExecutor()
+            {
+                config = serviceProvider.GetService<IConfiguration>(),
+                dataExtractor = serviceProvider.GetService<IDataExtractorService>(),
+                logger = serviceProvider.GetService<ILogger<ForkWatchJob>>(),
+                mapper = serviceProvider.GetService<IMapper>(),
+                cache = serviceProvider.GetService<IMemoryCache>(),
+                notificationManager = serviceProvider.GetService<INotificationManager>(),
+            };
+            executor.Execute();
+        }
+        // private Result<BlockInfoDTO> GetBlockInfo(RpcConfig rpcConfig, IDataExtractorService dataExtractor, IMapper mapper, string blockHash)
+        // {
+        //     var blockResult = dataExtractor.RpcCall<RpcBlockResult>(rpcConfig, "getblock", blockHash);
+        //     if (blockResult.HasFailed())
+        //     {
+        //         return Result<BlockInfoDTO>.Fail(blockResult.Messages.ToArray());
+        //     }
+
+        //     var block = mapper.Map<BlockInfoDTO>(blockResult.Value);
+        //     return Result<BlockInfoDTO>.Ok(block);
+        // }
+
+    }
+
+    class VirtualCheckpoint
+    {
+        public int Height;
+        public string Hash;
+    }
+
+    class WatchJobExecutor
+    {
+        const int VIRTUAL_FINALIZE_BLOCKS = 3;
+
+        public IConfiguration config;
+        public IDataExtractorService dataExtractor;
+        public ILogger<ForkWatchJob> logger;
+        public IMapper mapper;
+        public IMemoryCache cache;
+        public RpcConfig rpcConfig;
+        public INotificationManager notificationManager;
+
+        public void Execute()
+        {
+            rpcConfig = JobCommon.GetRpcConfig(config);
+            // compare chain tips
+            var lastSeenTips = cache.GetOrCreate<ChainTip[]>(Constants.LastSeenTipKey, entry => null);
+            ChainTip[] tips = null;
+            var shouldBacktrace = false;
+            Handle(Rpc<GetChainTipsResult>("getchaintips"), r =>
+            {
+                tips = r.Result;
+                var shouldSend = true;
+                var desc = "ForkWatch started";
+                if (lastSeenTips != null)
+                {
+                    (shouldSend, desc) = DiffTip(lastSeenTips, tips);
+                }
+                if (shouldSend)
+                {
+                    shouldBacktrace = true;
+                    var url = "";  // TODO: upload to pastbin and get url
+                    var message = $"{desc}\n{url}";
+                    notificationManager.TriggerHook(message);
+                }
+
+                cache.Set(Constants.LastSeenTipKey, tips);
+            });
+
+            if (tips == null || tips.Length == 0)
+            {
+                logger.LogWarning("ForkWatch: Got bad tip");
+            }
+
+            // short-circurit: no new block found
+            if (lastSeenTips != null && lastSeenTips[0].Hash == tips[0].Hash)
+            {
+                return;
+            }
+
+            // check virtual checkpoint rolled-back
+            var lastCheckpoint = cache.GetOrCreate<VirtualCheckpoint>(
+                Constants.VirtualCheckpointKey, entry => null);
+            if (lastCheckpoint != null)
+            {
+                bool foundReorg = false;
+                // check if the checkpoint is still in the main chain
+                Handle(Rpc<RpcResult>("getblockhash", lastCheckpoint.Height), r =>
+                {
+                    var hash = r.Result;
+                    foundReorg = (hash != lastCheckpoint.Hash);
+                    var message = $"ForkWatch: Virtual checkpoint {lastCheckpoint.Hash} at height {lastCheckpoint.Height} replaced by {hash}";
+                    notificationManager.TriggerHook(message);
+                });
+                // TODO: if foundReorg, move to "PREPARE"
+            }
+            // update virtual checkpoint
+            var height = tips[0].Height;
+            var toFinalize = height - VIRTUAL_FINALIZE_BLOCKS;
+            logger.LogWarning("getblockhash({0})", toFinalize);
+            Handle(Rpc<RpcResult>("getblockhash", toFinalize), r =>
+            {
+                var hash = r.Result;
+                cache.Set(Constants.VirtualCheckpointKey, new VirtualCheckpoint()
+                {
+                    Hash = hash,
+                    Height = toFinalize
+                });
+                notificationManager.TriggerHook(
+                    $"ForkWatch: new checkpoint {hash} at {toFinalize} ({-VIRTUAL_FINALIZE_BLOCKS}) tip: {height}");
+            });
+        }
+
+        Result<T> Rpc<T>(string name, params object[] args) where T : class
+        {
+            return dataExtractor.RpcCall<T>(rpcConfig, name, args);
+        }
+
+        Result<RpcResult> Rpc(string name, params object[] args)
+        {
+            return Rpc<RpcResult>(name, args);
+        }
+
+        void Handle<T>(Result<T> result, Action<T> action)
+        {
+            if (result.HasFailed())
+            {
+                logger.LogError(result.Messages.ToCommaSeparated());
+                return;
+            }
+            action(result.Value);
+        }
+
+        (bool, string) DiffTip(ChainTip[] a, ChainTip[] b)
+        {
+            var dictA = (from t in a where t.Status != "active" select t)
+                .ToDictionary(t => t.Hash, t => t);
+            var dictB = (from t in b where t.Status != "active" && t.Status != "headers-only" select t)
+                .ToDictionary(t => t.Hash, t => t);
+
+            var hashesA = new HashSet<string>(dictA.Keys);
+            var hashesB = new HashSet<string>(dictB.Keys);
+            var added = new HashSet<string>(hashesB);
+            added.ExceptWith(hashesA);
+
+            if (!added.Any())
+            {
+                return (false, null);
+            }
+
+            var branches = SimpleJson.SimpleJson.SerializeObject(
+                (from h in added select dictB[h]).ToList());
+            return (true, $"New branch: {branches}");
+        }
+
+        // n == 0: backtrace until meet main chain
+        // n > 0: backtrace n blocks
+        List<RpcBlockInfo> BacktraceBlocks(string tipHash, int n = 0)
+        {
+            var blocks = new List<RpcBlockInfo>();
+            var h = tipHash;
+            while (true)
+            {
+                var end = false;
+                Handle(Rpc<RpcBlockInfo>("getblock", h), b =>
+                {
+                    logger.LogInformation("Backtrace: {0} {1}", h, b.Confirmations);
+                    if (n == 0 && b.Confirmations >= 0)
+                    {
+                        end = true;
+                        return;
+                    }
+                    blocks.Append(b);
+                    h = b.PreviousBlockHash;
+                    if (blocks.Count == n)
+                    {
+                        end = true;
+                    }
+                });
+                if (end) break;
+            }
+            return blocks;
+        }
+    }
+}
\ No newline at end of file
diff --git a/CheckerApi/Program.cs b/CheckerApi/Program.cs
index 9a55375..e9eae19 100644
--- a/CheckerApi/Program.cs
+++ b/CheckerApi/Program.cs
@@ -106,6 +106,19 @@ public static void Main(string[] args)
                                 startAt: DateTimeOffset.UtcNow.AddSeconds(2)
                             );
                         }
+
+                        var forkWatchEnabled = config.GetValue<bool>("ForkWatch:Enable");
+                        if (forkWatchEnabled)
+                        {
+                            scheduler.AddJob<ForkWatchJob>(
+                                host,
+                                tb => tb.WithSimpleSchedule(x => x
+                                    .WithIntervalInSeconds(10)
+                                    .RepeatForever()
+                                ),
+                                startAt: DateTimeOffset.UtcNow.AddSeconds(3)
+                            );
+                        }
                     }
                 })
                 .Run();
diff --git a/CheckerApi/Utils/Constants.cs b/CheckerApi/Utils/Constants.cs
index aab5265..2ba89f0 100644
--- a/CheckerApi/Utils/Constants.cs
+++ b/CheckerApi/Utils/Constants.cs
@@ -6,5 +6,7 @@ public static class Constants
         public static string BtcBtgPriceKey { get; } = "BtcBtgPriceKey";
         public static string DifficultyKey { get; } = "DifficultyKey";
         public static string BlocksInfoKey { get; } = "BlocksInfoKey";
+        public static string LastSeenTipKey { get; } = "LastSeenTipKey";
+        public static string VirtualCheckpointKey { get; } = "VirtualCheckpointKey";
     }
 }