diff --git a/src/Filtering/Filter.coffee b/src/Filtering/Filter.coffee
index bcbd0e3602..17745f2fc7 100644
--- a/src/Filtering/Filter.coffee
+++ b/src/Filtering/Filter.coffee
@@ -78,10 +78,12 @@ Filter =
           else
             types = ['subject', 'name', 'filename', 'comment']
 
+        watch = /(?:^|;)\s*watch/.test filter
+
         # Hide the post (default case).
-        hide = !(hl or noti)
+        hide = !(hl or noti or watch)
 
-        filter = {isstring, regexp, boards, excludes, mask, hide, stub, hl, top, noti}
+        filter = {isstring, regexp, boards, excludes, mask, hide, stub, hl, top, noti, watch}
         if key is 'general'
           for type in types
             (@filters[type] or= []).push filter
@@ -119,11 +121,12 @@ Filter =
 
   test: (post, hideable=true) ->
     return post.filterResults if post.filterResults
-    hide = false
-    stub = true
-    hl   = undefined
-    top  = false
-    noti = false
+    hide  = false
+    stub  = true
+    hl    = undefined
+    top   = false
+    noti  = false
+    watch = false
     if QuoteYou.isYou(post)
       hideable = false
     mask = (if post.isReply then 2 else 1)
@@ -149,14 +152,16 @@ Filter =
             top or= filter.top
             if filter.noti
               noti = true
+            if filter.watch
+              watch = true
     if hide
       {hide, stub}
     else
-      {hl, top, noti}
+      {hl, top, noti, watch}
 
   node: ->
     return if @isClone
-    {hide, stub, hl, top, noti} = Filter.test @, (!@isFetchedQuote and (@isReply or g.VIEW is 'index'))
+    {hide, stub, hl, top, noti, watch} = Filter.test @, (!@isFetchedQuote and (@isReply or g.VIEW is 'index'))
     if hide
       if @isReply
         PostHiding.hide @, stub
@@ -168,6 +173,9 @@ Filter =
         $.addClass @nodes.root, hl...
     if noti and Unread.posts and (@ID > Unread.lastReadPost) and not QuoteYou.isYou(@)
       Unread.openNotification @, ' triggered a notification filter'
+    if watch and !ThreadWatcher.isWatched(@thread)
+      ThreadWatcher.add(@thread)
+
 
   catalog: ->
     return unless (url = g.SITE.urls.catalogJSON?(g.BOARD))
diff --git a/src/General/Settings/Filter-guide.html b/src/General/Settings/Filter-guide.html
index 02bba58050..477ef4f4f0 100644
--- a/src/General/Settings/Filter-guide.html
+++ b/src/General/Settings/Filter-guide.html
@@ -43,6 +43,12 @@
     Show a desktop notification instead of hiding.<br>
     For example: <code>notify;</code>.
   </li>
+  <li>
+    Add thread to thread watcher instead of hiding.<br/>
+    For example: <code>watch;</code><br/>
+    If you specify <code>boards</code> with this flag, the boards provided will be periodically scanned in the background for new threads.<br/>
+    If you do not specify boards, then it will scan every page you visit for matching threads/comments.
+  </li>
   <li>
     Filters in the "General" section apply to multiple fields, by default <code>subject,name,filename,comment</code>.<br>
     The fields can be specified with the <code>type</code> option, separated by commas.<br>
diff --git a/src/Monitoring/AutoWatcher.coffee b/src/Monitoring/AutoWatcher.coffee
new file mode 100644
index 0000000000..68aa3e474e
--- /dev/null
+++ b/src/Monitoring/AutoWatcher.coffee
@@ -0,0 +1,89 @@
+AutoWatcher =
+  init: ->
+    return unless Conf['Filter']
+
+    AutoWatcher.periodicScan()
+
+  periodicScan: ->
+    clearTimeout AutoWatcher.timeout
+
+    interval = 5 * $.MINUTE
+
+    now = Date.now()
+
+    unless Conf['autoWatchLastScan'] and (now - interval < Conf['autoWatchLastScan'])
+      AutoWatcher.scan()
+      $.set 'autoWatchLastScan', now
+    AutoWatcher.timeout = setTimeout AutoWatcher.periodicScan, interval
+
+  scan: ->
+    sitesAndBoards = (for own _, filters of Filter.filters
+      Object.keys(filter.boards) for filter in filters when filter.watch and filter.boards
+    ).flat(2).reduce (acc, i) ->
+      [_, k, v] = i.match(/(.*)\/(.*)/)
+      acc[k] ?= []
+      acc[k].push(v)
+      acc
+    , {}
+    for own rawSite, boards of sitesAndBoards
+      break unless site = g.sites[rawSite]
+      for boardID in boards
+        AutoWatcher.fetchCatalog(boardID, site, AutoWatcher.parseCatalog)
+
+  fetchCatalog: (boardID, site, cb) ->
+    return unless url = site.urls['catalogJSON']?({boardID})
+
+    ajax = if site.ID is g.SITE.ID then $.ajax else CrossOrigin.ajax
+
+    onLoadEnd = ->
+      cb.apply @, [site, boardID]
+
+    $.whenModified(
+      url,
+      'AutoWatcher'
+      onLoadEnd,
+      {timeout: $.MINUTE, ajax}
+    )
+
+  parseCatalog: (site, boardID) ->
+    addedThreads = false
+    rawCatalog = @.response.reduce ((acc, i, idx) ->
+      threads = for thread in i.threads
+        thread.extraData = {
+          page: idx + 1,
+          modified: thread.last_modified,
+          replies: thread.replies,
+          unread: thread.replies
+        }
+        if thread.last_replies
+          thread.extraData.last = thread.last_replies[thread.last_replies.length - 1].no
+        thread
+      acc.concat(threads)
+    ), []
+    for thread in rawCatalog
+      continue if ThreadWatcher.isWatchedRaw(boardID, thread.no)
+      parsedThread = site.Build.parseJSON(thread, {siteID: site.ID, boardID})
+
+      # Hacks for ThreadWatcher
+      parsedThread.isDead = false
+      parsedThread.board = {ID: boardID}
+      Object.assign(parsedThread, thread.extraData)
+
+      # I wish destructuring was actually pattern matching
+      {watch} = Filter.test(parsedThread)
+      continue unless watch
+
+      excerptName = (
+        parsedThread?.info?.subject or
+        parsedThread?.info?.comment.replace(/\n+/g, ' // ') or
+        parsedThread?.file?.name or
+        "No.#{parsedThread.ID}"
+      )
+      excerpt = "/#{boardID}/ - #{excerptName}"
+      excerpt = "#{excerpt[...70]}..." if excerpt.length > 73
+      data = Object.assign(thread.extraData, {excerpt})
+      ThreadWatcher.addRaw(boardID, parsedThread.ID, data, null, true)
+      addedThreads = true
+    # Check to see if we added any threads. If so, trigger a refresh AFTER we're done adding them all, to avoid spamming the API
+    # We already give the ThreadWatcher most of what it needs, this is just to get things like lastPage coloring
+    ThreadWatcher.buttonFetchAll() if addedThreads
diff --git a/src/Monitoring/ThreadWatcher.coffee b/src/Monitoring/ThreadWatcher.coffee
index 187f15dfb9..de77c42bf6 100644
--- a/src/Monitoring/ThreadWatcher.coffee
+++ b/src/Monitoring/ThreadWatcher.coffee
@@ -551,7 +551,7 @@ ThreadWatcher =
     data.excerpt = Get.threadExcerpt thread if thread.OP
     ThreadWatcher.addRaw boardID, threadID, data, cb
 
-  addRaw: (boardID, threadID, data, cb) ->
+  addRaw: (boardID, threadID, data, cb, skipRefresh = false) ->
     oldData = ThreadWatcher.db.get {boardID, threadID, defaultValue: $.dict()}
     delete oldData.last
     delete oldData.modified
@@ -559,6 +559,7 @@ ThreadWatcher =
     ThreadWatcher.db.set {boardID, threadID, val: oldData}, cb
     ThreadWatcher.refresh()
     thread = {siteID: g.SITE.ID, boardID, threadID, data, force: true}
+    return if skipRefresh
     if Conf['Show Page'] and !data.isDead
       ThreadWatcher.fetchBoard [thread]
     else if ThreadWatcher.unreadEnabled and Conf['Show Unread Count']
diff --git a/src/main/Main.coffee b/src/main/Main.coffee
index 0e79a5d736..2429a5324b 100644
--- a/src/main/Main.coffee
+++ b/src/main/Main.coffee
@@ -72,6 +72,7 @@ Main =
     Conf['archives'] = Redirect.archives
     Conf['selectedArchives'] = $.dict()
     Conf['cooldowns'] = $.dict()
+    Conf['autoWatchLastScan'] = null
     Conf['Index Sort'] = $.dict()
     Conf["Last Long Reply Thresholds #{i}"] = $.dict() for i in [0...2]
     Conf['siteProperties'] = $.dict()
@@ -521,7 +522,7 @@ Main =
       unless nodes[i]
         (cb() if cb)
         return
-      setTimeout softTask, 0 
+      setTimeout softTask, 0
 
     softTask()
 
@@ -698,6 +699,7 @@ Main =
     ['Thread Updater',            ThreadUpdater]
     ['Thread Watcher',            ThreadWatcher]
     ['Thread Watcher (Menu)',     ThreadWatcher.menu]
+    ['Auto Watcher',              AutoWatcher]
     ['Mark New IPs',              MarkNewIPs]
     ['Index Navigation',          Nav]
     ['Keybinds',                  Keybinds]