diff --git a/src/General/Config.coffee b/src/General/Config.coffee
index 2cd2abd02..d28934899 100755
--- a/src/General/Config.coffee
+++ b/src/General/Config.coffee
@@ -311,6 +311,10 @@ Config =
         true
         'Adds a shortcut for the thread watcher, hides the watcher by default, and makes it scroll with the page.'
       ]
+      'Mark New IPs': [
+        false
+        'Label each post from a new IP with the thread\'s current IP count.'
+      ]
 
     'Posting':
       'Quick Reply': [
diff --git a/src/General/Main.coffee b/src/General/Main.coffee
index 970227583..ee10abd8f 100755
--- a/src/General/Main.coffee
+++ b/src/General/Main.coffee
@@ -337,6 +337,7 @@ Main =
     ['Thread Updater',            ThreadUpdater]
     ['Thread Watcher',            ThreadWatcher]
     ['Thread Watcher (Menu)',     ThreadWatcher.menu]
+    ['Mark New IPs',              MarkNewIPs]
     ['Index Navigation',          Nav]
     ['Keybinds',                  Keybinds]
     ['Banner',                    Banner]
diff --git a/src/Monitoring/MarkNewIPs.coffee b/src/Monitoring/MarkNewIPs.coffee
new file mode 100644
index 000000000..7726a8e80
--- /dev/null
+++ b/src/Monitoring/MarkNewIPs.coffee
@@ -0,0 +1,46 @@
+MarkNewIPs =
+  init: ->
+    return if g.VIEW isnt 'thread' or !Conf['Mark New IPs']
+    Thread.callbacks.push
+      name: 'Mark New IPs'
+      cb:   @node
+
+  node: ->
+    MarkNewIPs.ipCount = @ipCount
+    MarkNewIPs.postIDs = @posts.keys.map (x) -> +x
+    $.on d, 'ThreadUpdate', MarkNewIPs.onUpdate
+
+  onUpdate: (e) ->
+    {ipCount, newPosts} = e.detail
+    {postIDs} = ThreadUpdater
+    return unless ipCount?
+    if newPosts.length
+      obj = {}
+      obj[x] = true for x in MarkNewIPs.postIDs
+      added = 0
+      added++ for x in postIDs when not (x of obj)
+      removed = MarkNewIPs.postIDs.length + added - postIDs.length
+      switch ipCount - MarkNewIPs.ipCount
+        when added
+          i = MarkNewIPs.ipCount
+          for fullID in newPosts
+            MarkNewIPs.mark g.posts[fullID], ++i
+        when -removed
+          for fullID in newPosts
+            $.addClass g.posts[fullID].nodes.root, 'old-ip'
+    MarkNewIPs.ipCount = ipCount
+    MarkNewIPs.postIDs = postIDs
+
+  mark: (post, ipCount) ->
+    suffix = switch ipCount
+      when 1 then 'st'
+      when 2 then 'nd'
+      when 3 then 'rd'
+      else 'th'
+    counter = $.el 'span',
+      className: 'ip-counter'
+      textContent: "(#{ipCount})"
+      title: "This is the #{ipCount}#{suffix} IP in the thread."
+    nameBlock = $ '.nameBlock', post.nodes.info
+    $.add nameBlock, [$.tn(' '), counter]
+    $.addClass post.nodes.root, 'new-ip'
diff --git a/src/Monitoring/ThreadUpdater.coffee b/src/Monitoring/ThreadUpdater.coffee
index b6dec04f1..b94cab67f 100755
--- a/src/Monitoring/ThreadUpdater.coffee
+++ b/src/Monitoring/ThreadUpdater.coffee
@@ -340,6 +340,8 @@ ThreadUpdater =
       ipCountEl.previousSibling.textContent = ipCountEl.previousSibling.textContent.replace(/\b(?:is|are)\b/, if OP.unique_ips is 1 then 'is' else 'are')
       ipCountEl.nextSibling.textContent = ipCountEl.nextSibling.textContent.replace(/\bposters?\b/, if OP.unique_ips is 1 then 'poster' else 'posters')
 
+    ThreadUpdater.postIDs = index
+
     $.event 'ThreadUpdate',
       404: false
       threadID: ThreadUpdater.thread.fullID