diff --git a/services/document-updater/app.coffee b/services/document-updater/app.coffee
index af0ad242c2..df26b81a2f 100644
--- a/services/document-updater/app.coffee
+++ b/services/document-updater/app.coffee
@@ -46,6 +46,7 @@ app.post   '/project/:project_id/doc/:doc_id/flush', HttpController.flushDocIfLo
 app.delete '/project/:project_id/doc/:doc_id',       HttpController.flushAndDeleteDoc
 app.delete '/project/:project_id',                   HttpController.deleteProject
 app.post   '/project/:project_id/flush',             HttpController.flushProject
+app.post   '/project/:project_id/track_changes',     HttpController.setTrackChanges
 
 app.get '/total', (req, res)->
 	timer = new Metrics.Timer("http.allDocList")	
diff --git a/services/document-updater/app/coffee/ChangesTracker.coffee b/services/document-updater/app/coffee/ChangesTracker.coffee
new file mode 100644
index 0000000000..8bc4cf9380
--- /dev/null
+++ b/services/document-updater/app/coffee/ChangesTracker.coffee
@@ -0,0 +1,457 @@
+load = (EventEmitter) ->
+	class ChangesTracker extends EventEmitter
+		# The purpose of this class is to track a set of inserts and deletes to a document, like
+		# track changes in Word. We store these as a set of ShareJs style ranges:
+		#   {i: "foo", p: 42} # Insert 'foo' at offset 42
+		#   {d: "bar", p: 37} # Delete 'bar' at offset 37
+		# We only track the inserts and deletes, not the whole document, but by being given all
+		# updates that are applied to a document, we can update these appropriately.
+		# 
+		# Note that the set of inserts and deletes we store applies to the document as-is at the moment.
+		# So inserts correspond to text which is in the document, while deletes correspond to text which
+		# is no longer there, so their lengths do not affect the position of later offsets.
+		# E.g.
+		#             this is the current text of the document
+		#                         |-----|            |
+		#  {i: "current ", p:12} -^                   ^- {d: "old ", p: 31}
+		#
+		# Track changes rules (should be consistent with Word):
+		#   * When text is inserted at a delete, the text goes to the left of the delete
+		#       I.e. "foo|bar" -> "foobaz|bar", where | is the delete, and 'baz' is inserted
+		#   * Deleting content flagged as 'inserted' does not create a new delete marker, it only
+		#     removes the insert marker. E.g.
+		#       * "abdefghijkl"        -> "abfghijkl"        when 'de' is deleted. No delete marker added
+		#           |---| <- inserted       |-| <- inserted
+		#       * Deletes overlapping regular text and inserted text will insert a delete marker for the
+		#         regular text:
+		#         "abcdefghijkl"    ->    "abcdejkl"   when 'fghi' is deleted
+		#           |----|                  |--||
+		#           ^- inserted 'bcdefg'      \ ^- deleted 'hi'
+		#                                      \--inserted 'bcde'
+		#   * Deletes overlapping other deletes are merged. E.g.
+		#      "abcghijkl"        ->   "ahijkl"     when 'bcg is deleted'
+		#          | <- delete 'def'     | <- delete 'bcdefg'
+		#   * Deletes by another user will consume deletes by the first user
+		#   * Inserts by another user will not combine with inserts by the first user. If they are in the
+		#     middle of a previous insert by the first user, the original insert will be split into two.
+		constructor: (@changes = [], @comments = []) ->
+			# Change objects have the following structure:
+			# {
+			#   id: ... # Uniquely generated by us
+			#   op: { # ShareJs style op tracking the offset (p) and content inserted (i) or deleted (d)
+			#     i: "..."
+			#     p: 42
+			#   }
+			# }
+			#
+			# Ids are used to uniquely identify a change, e.g. for updating it in the database, or keeping in
+			# sync with Ace ranges.
+			@id = 0
+		
+		addComment: (offset, length, metadata) ->
+			# TODO: Don't allow overlapping comments?
+			@comments.push comment = {
+				id: @_newId()
+				offset, length, metadata
+			}
+			@emit "comment:added", comment
+			return comment
+		
+		getComment: (comment_id) ->
+			comment = null
+			for c in @comments
+				if c.id == comment_id
+					comment = c
+					break
+			return comment
+		
+		resolveCommentId: (comment_id, resolved_data) ->
+			comment = @getComment(comment_id)
+			return if !comment?
+			comment.metadata.resolved = true
+			comment.metadata.resolved_data = resolved_data
+			@emit "comment:resolved", comment
+		
+		unresolveCommentId: (comment_id) ->
+			comment = @getComment(comment_id)
+			return if !comment?
+			comment.metadata.resolved = false
+			@emit "comment:unresolved", comment
+		
+		removeCommentId: (comment_id) ->
+			comment = @getComment(comment_id)
+			return if !comment?
+			@comments = @comments.filter (c) -> c.id != comment_id
+			@emit "comment:removed", comment
+		
+		getChange: (change_id) ->
+			change = null
+			for c in @changes
+				if c.id == change_id
+					change = c
+					break
+			return change
+
+		removeChangeId: (change_id) ->
+			change = @getChange(change_id)
+			return if !change?
+			@_removeChange(change)
+
+		applyOp: (op, metadata = {}) ->
+			metadata.ts ?= new Date()
+			# Apply an op that has been applied to the document to our changes to keep them up to date
+			if op.i?
+				@applyInsertToChanges(op, metadata)
+				@applyInsertToComments(op)
+			else if op.d?
+				@applyDeleteToChanges(op, metadata)
+				@applyDeleteToComments(op)
+		
+		applyInsertToComments: (op) ->
+			for comment in @comments
+				if op.p <= comment.offset
+					comment.offset += op.i.length
+					@emit "comment:moved", comment
+				else if op.p < comment.offset + comment.length
+					comment.length += op.i.length
+					@emit "comment:moved", comment
+
+		applyDeleteToComments: (op) ->
+			op_start = op.p
+			op_length = op.d.length
+			op_end = op.p + op_length
+			for comment in @comments
+				comment_end = comment.offset + comment.length
+				if op_end <= comment.offset
+					# delete is fully before comment
+					comment.offset -= op_length
+					@emit "comment:moved", comment
+				else if op_start >= comment_end
+					# delete is fully after comment, nothing to do
+				else
+					# delete and comment overlap
+					delete_length_before = Math.max(0, comment.offset - op_start)
+					delete_length_after = Math.max(0, op_end - comment_end)
+					delete_length_overlapping = op_length - delete_length_before - delete_length_after
+					comment.offset = Math.min(comment.offset, op_start)
+					comment.length -= delete_length_overlapping
+					@emit "comment:moved", comment
+
+		applyInsertToChanges: (op, metadata) ->
+			op_start = op.p
+			op_length = op.i.length
+			op_end = op.p + op_length
+
+			already_merged = false
+			previous_change = null
+			moved_changes = []
+			remove_changes = []
+			new_changes = []
+			for change in @changes
+				change_start = change.op.p
+				
+				if change.op.d?
+					# Shift any deletes after this along by the length of this insert
+					if op_start < change_start
+						change.op.p += op_length
+						moved_changes.push change
+					else if op_start == change_start
+						# If the insert matches the start of the delete, just remove it from the delete instead
+						if change.op.d.length >= op.i.length and change.op.d.slice(0, op.i.length) == op.i
+							change.op.d = change.op.d.slice(op.i.length)
+							change.op.p += op.i.length
+							if change.op.d == ""
+								remove_changes.push change
+							else
+								moved_changes.push change
+							already_merged = true
+						else
+							change.op.p += op_length
+							moved_changes.push change
+				else if change.op.i?
+					change_end = change_start + change.op.i.length
+					is_change_overlapping = (op_start >= change_start and op_start <= change_end)
+					
+					# Only merge inserts if they are from the same user
+					is_same_user = metadata.user_id == change.metadata.user_id
+					
+					# If there is a delete at the start of the insert, and we're inserting
+					# at the start, we SHOULDN'T merge since the delete acts as a partition.
+					# The previous op will be the delete, but it's already been shifted by this insert
+					#
+					# I.e.
+					# Originally: |-- existing insert --|
+					#             | <- existing delete at same offset
+					#
+					# Now:        |-- existing insert --| <- not shifted yet
+					#             |-- this insert --|| <- existing delete shifted along to end of this op
+					# 
+					# After:                         |-- existing insert --|  
+					#             |-- this insert --|| <- existing delete
+					# 
+					# Without the delete, the inserts would be merged.
+					is_insert_blocked_by_delete = (previous_change? and previous_change.op.d? and previous_change.op.p == op_end)
+
+					# If the insert is overlapping another insert, either at the beginning in the middle or touching the end,
+					# then we merge them into one.
+					if @track_changes and
+							is_change_overlapping and
+							!is_insert_blocked_by_delete and
+							!already_merged and 
+							is_same_user
+						offset = op_start - change_start
+						change.op.i = change.op.i.slice(0, offset) + op.i + change.op.i.slice(offset)
+						change.metadata.ts = metadata.ts
+						already_merged = true
+						moved_changes.push change
+					else if op_start <= change_start
+						# If we're fully before the other insert we can just shift the other insert by our length.
+						# If they are touching, and should have been merged, they will have been above.
+						# If not merged above, then it must be blocked by a delete, and will be after this insert, so we shift it along as well
+						change.op.p += op_length
+						moved_changes.push change
+					else if (!is_same_user or !@track_changes) and change_start < op_start < change_end
+						# This user is inserting inside a change by another user, so we need to split the
+						# other user's change into one before and after this one.
+						offset = op_start - change_start
+						before_content = change.op.i.slice(0, offset)
+						after_content = change.op.i.slice(offset)
+						
+						# The existing change can become the 'before' change
+						change.op.i = before_content
+						moved_changes.push change
+						
+						# Create a new op afterwards
+						after_change = {
+							op: {
+								i: after_content
+								p: change_start + offset + op_length
+							}
+							metadata: {}
+						}
+						after_change.metadata[key] = value for key, value of change.metadata
+						new_changes.push after_change
+						
+				previous_change = change
+
+			if @track_changes and !already_merged
+				@_addOp op, metadata
+			for {op, metadata} in new_changes
+				@_addOp op, metadata
+		
+			for change in remove_changes
+				@_removeChange change
+			
+			if moved_changes.length > 0
+				@emit "changes:moved", moved_changes
+		
+		applyDeleteToChanges: (op, metadata) ->
+			op_start = op.p
+			op_length = op.d.length
+			op_end = op.p + op_length
+			remove_changes = []
+			moved_changes = []
+			
+			# We might end up modifying our delete op if it merges with existing deletes, or cancels out
+			# with an existing insert. Since we might do multiple modifications, we record them and do
+			# all the modifications after looping through the existing changes, so as not to mess up the
+			# offset indexes as we go.
+			op_modifications = []
+			for change in @changes
+				if change.op.i?
+					change_start = change.op.p
+					change_end = change_start + change.op.i.length
+					if op_end <= change_start
+						# Shift ops after us back by our length
+						change.op.p -= op_length
+						moved_changes.push change
+					else if op_start >= change_end
+						# Delete is after insert, nothing to do
+					else
+						# When the new delete overlaps an insert, we should remove the part of the insert that
+						# is now deleted, and also remove the part of the new delete that overlapped. I.e.
+						# the two cancel out where they overlap.
+						if op_start >= change_start
+							#                            |-- existing insert --|
+							# insert_remaining_before -> |.....||--   new delete   --|
+							delete_remaining_before = ""
+							insert_remaining_before = change.op.i.slice(0, op_start - change_start)
+						else
+							# delete_remaining_before -> |.....||-- existing insert --|
+							#                            |-- new delete   --|
+							delete_remaining_before = op.d.slice(0, change_start - op_start)
+							insert_remaining_before = ""
+
+						if op_end <= change_end
+							#    |--  existing insert  --|
+							# |--  new delete   --||.....| <- insert_remaining_after
+							delete_remaining_after = ""
+							insert_remaining_after = change.op.i.slice(op_end - change_start)
+						else
+							# |--  existing insert  --||.....| <- delete_remaining_after
+							#            |--  new delete   --|
+							delete_remaining_after = op.d.slice(change_end - op_start)
+							insert_remaining_after = ""
+
+						insert_remaining = insert_remaining_before + insert_remaining_after
+						if insert_remaining.length > 0
+							change.op.i = insert_remaining
+							change.op.p = Math.min(change_start, op_start)
+							change.metadata.ts = metadata.ts
+							moved_changes.push change
+						else
+							remove_changes.push change
+
+						# We know what we want to preserve of our delete op before (delete_remaining_before) and what we want to preserve
+						# afterwards (delete_remaining_before). Now we need to turn that into a modification which deletes the 
+						# chunk in the middle not covered by these.
+						delete_removed_length = op.d.length - delete_remaining_before.length - delete_remaining_after.length
+						delete_removed_start = delete_remaining_before.length
+						modification = {
+							d: op.d.slice(delete_removed_start, delete_removed_start + delete_removed_length)
+							p: delete_removed_start
+						}
+						if modification.d.length > 0
+							op_modifications.push modification
+				else if change.op.d?
+					change_start = change.op.p
+					if op_end < change_start or (!@track_changes and op_end == change_start)
+						# Shift ops after us back by our length.
+						# If we're tracking changes, it must be strictly before, since we'll merge 
+						# below if they are touching. Otherwise, touching is fine.
+						change.op.p -= op_length
+						moved_changes.push change
+					else if op_start <= change_start <= op_end
+						if @track_changes
+							# If we overlap a delete, add it in our content, and delete the existing change.
+							# It's easier to do it this way, rather than modifying the existing delete in case
+							# we overlap many deletes and we'd need to track that. We have a workaround to
+							# update the delete in place if possible below.
+							offset = change_start - op_start
+							op_modifications.push { i: change.op.d, p: offset }
+							remove_changes.push change
+						else
+							change.op.p = op_start
+							moved_changes.push change
+
+			# Copy rather than modify because we still need to apply it to comments
+			op = {
+				p: op.p
+				d: @_applyOpModifications(op.d, op_modifications)
+			}
+
+			for change in remove_changes
+				# This is a bit of hack to avoid removing one delete and replacing it with another.
+				# If we don't do this, it causes the UI to flicker
+				if op.d.length > 0 and change.op.d? and op.p <= change.op.p <= op.p + op.d.length
+					change.op.p = op.p
+					change.op.d = op.d
+					change.metadata = metadata
+					moved_changes.push change
+					op.d = "" # stop it being added
+				else
+					@_removeChange change
+
+			if @track_changes and op.d.length > 0
+				@_addOp op, metadata
+			else
+				# It's possible that we deleted an insert between two other inserts. I.e.
+				# If we delete 'user_2 insert' in:
+				#   |-- user_1 insert --||-- user_2 insert --||-- user_1 insert --|
+				# it becomes:
+				#   |-- user_1 insert --||-- user_1 insert --|
+				# We need to merge these together again
+				results = @_scanAndMergeAdjacentUpdates()
+				moved_changes = moved_changes.concat(results.moved_changes)
+				for change in results.remove_changes
+					@_removeChange change
+					moved_changes = moved_changes.filter (c) -> c != change
+			
+			if moved_changes.length > 0
+				@emit "changes:moved", moved_changes
+
+		_newId: () ->
+			(@id++).toString()
+
+		_addOp: (op, metadata) ->
+			change = {
+				id: @_newId()
+				op: op
+				metadata: metadata
+			}
+			@changes.push change
+
+			# Keep ops in order of offset, with deletes before inserts
+			@changes.sort (c1, c2) ->
+				result = c1.op.p - c2.op.p
+				if result != 0
+					return result
+				else if c1.op.i? and c2.op.d?
+					return 1
+				else
+					return -1
+
+			if op.d?
+				@emit "delete:added", change
+			else if op.i?
+				@emit "insert:added", change
+		
+		_removeChange: (change) ->
+			@changes = @changes.filter (c) -> c.id != change.id
+			if change.op.d?
+				@emit "delete:removed", change
+			else if change.op.i?
+				@emit "insert:removed", change
+			
+		_applyOpModifications: (content, op_modifications) ->
+			# Put in descending position order, with deleting first if at the same offset 
+			# (Inserting first would modify the content that the delete will delete)
+			op_modifications.sort (a, b) ->
+				result = b.p - a.p 
+				if result != 0
+					return result
+				else if a.i? and b.d?
+					return 1
+				else
+					return -1
+
+			for modification in op_modifications
+				if modification.i?
+					content = content.slice(0, modification.p) + modification.i + content.slice(modification.p)
+				else if modification.d?
+					if content.slice(modification.p, modification.p + modification.d.length) != modification.d
+						throw new Error("deleted content does not match. content: #{JSON.stringify(content)}; modification: #{JSON.stringify(modification)}")
+					content = content.slice(0, modification.p) + content.slice(modification.p + modification.d.length)
+			return content
+		
+		_scanAndMergeAdjacentUpdates: () ->
+			# This should only need calling when deleting an update between two
+			# other updates. There's no other way to get two adjacent updates from the
+			# same user, since they would be merged on insert.
+			previous_change = null
+			remove_changes = []
+			moved_changes = []
+			for change in @changes
+				if previous_change?.op.i? and change.op.i?
+					previous_change_end = previous_change.op.p + previous_change.op.i.length
+					previous_change_user_id = previous_change.metadata.user_id
+					change_start = change.op.p
+					change_user_id = change.metadata.user_id
+					if previous_change_end == change_start and previous_change_user_id == change_user_id
+						remove_changes.push change
+						previous_change.op.i += change.op.i
+						moved_changes.push previous_change
+				else if previous_change?.op.d? and change.op.d? and previous_change.op.p == change.op.p
+					# Merge adjacent deletes
+					previous_change.op.d += change.op.d
+					remove_changes.push change
+					moved_changes.push previous_change
+				else # Only update to the current change if we haven't removed it.
+					previous_change = change
+			return { moved_changes, remove_changes }
+
+if define?
+	define ["utils/EventEmitter"], load
+else
+	EventEmitter = require("events").EventEmitter
+	module.exports = load(EventEmitter)
\ No newline at end of file
diff --git a/services/document-updater/app/coffee/DocumentManager.coffee b/services/document-updater/app/coffee/DocumentManager.coffee
index ebbdc3a66e..9c7277c469 100644
--- a/services/document-updater/app/coffee/DocumentManager.coffee
+++ b/services/document-updater/app/coffee/DocumentManager.coffee
@@ -3,7 +3,8 @@ PersistenceManager = require "./PersistenceManager"
 DiffCodec = require "./DiffCodec"
 logger = require "logger-sharelatex"
 Metrics = require "./Metrics"
-TrackChangesManager = require "./TrackChangesManager"
+HistoryManager = require "./HistoryManager"
+WebRedisManager = require "./WebRedisManager"
 
 module.exports = DocumentManager =
 	getDoc: (project_id, doc_id, _callback = (error, lines, version, alreadyLoaded) ->) ->
@@ -12,18 +13,18 @@ module.exports = DocumentManager =
 			timer.done()
 			_callback(args...)
 
-		RedisManager.getDoc project_id, doc_id, (error, lines, version) ->
+		RedisManager.getDoc project_id, doc_id, (error, lines, version, track_changes, track_changes_entries) ->
 			return callback(error) if error?
 			if !lines? or !version?
-				logger.log project_id: project_id, doc_id: doc_id, "doc not in redis so getting from persistence API"
-				PersistenceManager.getDoc project_id, doc_id, (error, lines, version) ->
+				logger.log {project_id, doc_id, track_changes}, "doc not in redis so getting from persistence API"
+				PersistenceManager.getDoc project_id, doc_id, (error, lines, version, track_changes, track_changes_entries) ->
 					return callback(error) if error?
-					logger.log project_id: project_id, doc_id: doc_id, lines: lines, version: version, "got doc from persistence API"
-					RedisManager.putDocInMemory project_id, doc_id, lines, version, (error) ->
+					logger.log {project_id, doc_id, lines, version, track_changes}, "got doc from persistence API"
+					RedisManager.putDocInMemory project_id, doc_id, lines, version, track_changes, track_changes_entries, (error) ->
 						return callback(error) if error?
-						callback null, lines, version, false
+						callback null, lines, version, track_changes, track_changes_entries, false
 			else
-				callback null, lines, version, true
+				callback null, lines, version, track_changes, track_changes_entries, true
 
 	getDocAndRecentOps: (project_id, doc_id, fromVersion, _callback = (error, lines, version, recentOps) ->) ->
 		timer = new Metrics.Timer("docManager.getDocAndRecentOps")
@@ -50,7 +51,7 @@ module.exports = DocumentManager =
 			return callback(new Error("No lines were provided to setDoc"))
 
 		UpdateManager = require "./UpdateManager"
-		DocumentManager.getDoc project_id, doc_id, (error, oldLines, version, alreadyLoaded) ->
+		DocumentManager.getDoc project_id, doc_id, (error, oldLines, version, track_changes, alreadyLoaded) ->
 			return callback(error) if error?
 			
 			if oldLines? and oldLines.length > 0 and oldLines[0].text?
@@ -89,14 +90,14 @@ module.exports = DocumentManager =
 		callback = (args...) ->
 			timer.done()
 			_callback(args...)
-		RedisManager.getDoc project_id, doc_id, (error, lines, version) ->
+		RedisManager.getDoc project_id, doc_id, (error, lines, version, track_changes, track_changes_entries) ->
 			return callback(error) if error?
 			if !lines? or !version?
 				logger.log project_id: project_id, doc_id: doc_id, "doc is not loaded so not flushing"
 				callback null  # TODO: return a flag to bail out, as we go on to remove doc from memory?
 			else
 				logger.log project_id: project_id, doc_id: doc_id, version: version, "flushing doc"
-				PersistenceManager.setDoc project_id, doc_id, lines, version, (error) ->
+				PersistenceManager.setDoc project_id, doc_id, lines, version, track_changes, track_changes_entries, (error) ->
 					return callback(error) if error?
 					callback null
 
@@ -111,13 +112,19 @@ module.exports = DocumentManager =
 			
 			# Flush in the background since it requires and http request
 			# to track changes
-			TrackChangesManager.flushDocChanges project_id, doc_id, (err) ->
+			HistoryManager.flushDocChanges project_id, doc_id, (err) ->
 				if err?
 					logger.err {err, project_id, doc_id}, "error flushing to track changes"
 
 			RedisManager.removeDocFromMemory project_id, doc_id, (error) ->
 				return callback(error) if error?
 				callback null
+	
+	setTrackChanges: (project_id, doc_id, track_changes_on, callback = (error) ->) ->
+		RedisManager.setTrackChanges project_id, doc_id, track_changes_on, (error) ->
+			return callback(error) if error?
+			WebRedisManager.sendData {project_id, doc_id, track_changes_on}
+			callback()
 
 	getDocWithLock: (project_id, doc_id, callback = (error, lines, version) ->) ->
 		UpdateManager = require "./UpdateManager"
@@ -138,3 +145,7 @@ module.exports = DocumentManager =
 	flushAndDeleteDocWithLock: (project_id, doc_id, callback = (error) ->) ->
 		UpdateManager = require "./UpdateManager"
 		UpdateManager.lockUpdatesAndDo DocumentManager.flushAndDeleteDoc, project_id, doc_id, callback
+
+	setTrackChangesWithLock: (project_id, doc_id, track_changes_on, callback = (error) ->) ->
+		UpdateManager = require "./UpdateManager"
+		UpdateManager.lockUpdatesAndDo DocumentManager.setTrackChanges, project_id, doc_id, track_changes_on, callback
\ No newline at end of file
diff --git a/services/document-updater/app/coffee/HistoryManager.coffee b/services/document-updater/app/coffee/HistoryManager.coffee
new file mode 100644
index 0000000000..637fd2cb5f
--- /dev/null
+++ b/services/document-updater/app/coffee/HistoryManager.coffee
@@ -0,0 +1,44 @@
+settings = require "settings-sharelatex"
+request  = require "request"
+logger = require "logger-sharelatex"
+async = require "async"
+WebRedisManager = require "./WebRedisManager"
+
+module.exports = HistoryManager =
+	flushDocChanges: (project_id, doc_id, callback = (error) ->) ->
+		if !settings.apis?.trackchanges?
+			logger.warn doc_id: doc_id, "track changes API is not configured, so not flushing"
+			return callback()
+
+		url = "#{settings.apis.trackchanges.url}/project/#{project_id}/doc/#{doc_id}/flush"
+		logger.log project_id: project_id, doc_id: doc_id, url: url, "flushing doc in track changes api"
+		request.post url, (error, res, body)->
+			if error?
+				return callback(error)
+			else if res.statusCode >= 200 and res.statusCode < 300
+				return callback(null)
+			else
+				error = new Error("track changes api returned a failure status code: #{res.statusCode}")
+				return callback(error)
+
+	FLUSH_EVERY_N_OPS: 50
+	pushUncompressedHistoryOps: (project_id, doc_id, ops = [], callback = (error) ->) ->
+		if ops.length == 0
+			return callback()
+		WebRedisManager.pushUncompressedHistoryOps project_id, doc_id, ops, (error, length) ->
+			return callback(error) if error?
+			# We want to flush every 50 ops, i.e. 50, 100, 150, etc
+			# Find out which 'block' (i.e. 0-49, 50-99) we were in before and after pushing these
+			# ops. If we've changed, then we've gone over a multiple of 50 and should flush.
+			# (Most of the time, we will only hit 50 and then flushing will put us back to 0)
+			previousLength = length - ops.length
+			prevBlock = Math.floor(previousLength / HistoryManager.FLUSH_EVERY_N_OPS)
+			newBlock  = Math.floor(length / HistoryManager.FLUSH_EVERY_N_OPS)
+			if newBlock != prevBlock
+				# Do this in the background since it uses HTTP and so may be too
+				# slow to wait for when processing a doc update.
+				logger.log length: length, doc_id: doc_id, project_id: project_id, "flushing track changes api"
+				HistoryManager.flushDocChanges project_id, doc_id,  (error) ->
+					if error?
+						logger.error err: error, doc_id: doc_id, project_id: project_id, "error flushing doc to track changes api"
+			callback()
\ No newline at end of file
diff --git a/services/document-updater/app/coffee/HttpController.coffee b/services/document-updater/app/coffee/HttpController.coffee
index ee6359b104..0366746d56 100644
--- a/services/document-updater/app/coffee/HttpController.coffee
+++ b/services/document-updater/app/coffee/HttpController.coffee
@@ -96,3 +96,15 @@ module.exports = HttpController =
 			return next(error) if error?
 			logger.log project_id: project_id, "deleted project via http"
 			res.send 204 # No Content
+	
+	setTrackChanges: (req, res, next = (error) ->) ->
+		project_id = req.params.project_id
+		track_changes_on = req.body.on
+		if !track_changes_on?
+			return res.send 400
+		track_changes_on = !!track_changes_on # Make boolean
+		logger.log {project_id, track_changes_on}, "turning on track changes via http"
+		ProjectManager.setTrackChangesWithLocks project_id, track_changes_on, (error) ->
+			return next(error) if error?
+			res.send 204
+
diff --git a/services/document-updater/app/coffee/PersistenceManager.coffee b/services/document-updater/app/coffee/PersistenceManager.coffee
index 605425eb5e..8d5578b4cf 100644
--- a/services/document-updater/app/coffee/PersistenceManager.coffee
+++ b/services/document-updater/app/coffee/PersistenceManager.coffee
@@ -12,14 +12,14 @@ MAX_HTTP_REQUEST_LENGTH = 5000 # 5 seconds
 
 module.exports = PersistenceManager =
 	getDoc: (project_id, doc_id, callback = (error, lines, version) ->) ->
-		PersistenceManager.getDocFromWeb project_id, doc_id, (error, lines) ->
+		PersistenceManager.getDocFromWeb project_id, doc_id, (error, lines, track_changes, track_changes_entries) ->
 			return callback(error) if error?
 			PersistenceManager.getDocVersionInMongo doc_id, (error, version) ->
 				return callback(error) if error?
-				callback null, lines, version
+				callback null, lines, version, track_changes, track_changes_entries
 
-	setDoc: (project_id, doc_id, lines, version, callback = (error) ->) ->
-		PersistenceManager.setDocInWeb project_id, doc_id, lines, (error) ->
+	setDoc: (project_id, doc_id, lines, version, track_changes, track_changes_entries, callback = (error) ->) ->
+		PersistenceManager.setDocInWeb project_id, doc_id, lines, track_changes, track_changes_entries, (error) ->
 			return callback(error) if error?
 			PersistenceManager.setDocVersionInMongo doc_id, version, (error) ->
 				return callback(error) if error?
@@ -50,13 +50,13 @@ module.exports = PersistenceManager =
 					body = JSON.parse body
 				catch e
 					return callback(e)
-				return callback null, body.lines
+				return callback null, body.lines, body.track_changes, body.track_changes_entries
 			else if res.statusCode == 404
 				return callback(new Errors.NotFoundError("doc not not found: #{url}"))
 			else
 				return callback(new Error("error accessing web API: #{url} #{res.statusCode}"))
 
-	setDocInWeb: (project_id, doc_id, lines, _callback = (error) ->) ->
+	setDocInWeb: (project_id, doc_id, lines, track_changes, track_changes_entries, _callback = (error) ->) ->
 		timer = new Metrics.Timer("persistenceManager.setDoc")
 		callback = (args...) ->
 			timer.done()
@@ -68,6 +68,8 @@ module.exports = PersistenceManager =
 			method: "POST"
 			body: JSON.stringify
 				lines: lines
+				track_changes: track_changes
+				track_changes_entries: track_changes_entries
 			headers:
 				"content-type": "application/json"
 			auth:
diff --git a/services/document-updater/app/coffee/ProjectManager.coffee b/services/document-updater/app/coffee/ProjectManager.coffee
index f0f62b6d1b..a38fe08397 100644
--- a/services/document-updater/app/coffee/ProjectManager.coffee
+++ b/services/document-updater/app/coffee/ProjectManager.coffee
@@ -57,4 +57,30 @@ module.exports = ProjectManager =
 				else
 					callback(null)
 
+	setTrackChangesWithLocks: (project_id, track_changes_on, _callback = (error) ->) ->
+		timer = new Metrics.Timer("projectManager.toggleTrackChangesWithLocks")
+		callback = (args...) ->
+			timer.done()
+			_callback(args...)
+
+		RedisManager.getDocIdsInProject project_id, (error, doc_ids) ->
+			return callback(error) if error?
+			jobs = []
+			errors = []
+			for doc_id in (doc_ids or [])
+				do (doc_id) ->
+					jobs.push (callback) ->
+						DocumentManager.setTrackChangesWithLock project_id, doc_id, track_changes_on, (error) ->
+							if error?
+								logger.error {err: error, project_id, doc_ids, track_changes_on}, "error toggle track changes for doc"
+								errors.push(error)
+							callback()
+			# TODO: If no docs, turn on track changes in Mongo manually
+
+			logger.log {project_id, doc_ids, track_changes_on}, "toggling track changes for docs"
+			async.series jobs, () ->
+				if errors.length > 0
+					callback new Error("Errors toggling track changes for docs. See log for details")
+				else
+					callback(null)
 		
diff --git a/services/document-updater/app/coffee/RedisKeyBuilder.coffee b/services/document-updater/app/coffee/RedisKeyBuilder.coffee
index 0e9e59e8f1..c09fb43f00 100644
--- a/services/document-updater/app/coffee/RedisKeyBuilder.coffee
+++ b/services/document-updater/app/coffee/RedisKeyBuilder.coffee
@@ -34,6 +34,10 @@ module.exports = RedisKeyBuilder =
 		return (key_schema) -> key_schema.uncompressedHistoryOp({doc_id})
 	pendingUpdates: ({doc_id}) ->
 		return (key_schema) -> key_schema.pendingUpdates({doc_id})
+	trackChangesEnabled: ({doc_id}) ->
+		return (key_schema) -> key_schema.trackChangesEnabled({doc_id})
+	trackChangesEntries: ({doc_id}) ->
+		return (key_schema) -> key_schema.trackChangesEntries({doc_id})
 	docsInProject: ({project_id}) ->
 		return (key_schema) -> key_schema.docsInProject({project_id})
 	docsWithHistoryOps: ({project_id}) ->
diff --git a/services/document-updater/app/coffee/RedisManager.coffee b/services/document-updater/app/coffee/RedisManager.coffee
index 87e31b7826..6ee764cb7e 100644
--- a/services/document-updater/app/coffee/RedisManager.coffee
+++ b/services/document-updater/app/coffee/RedisManager.coffee
@@ -13,7 +13,7 @@ minutes = 60 # seconds for Redis expire
 module.exports = RedisManager =
 	rclient: rclient
 
-	putDocInMemory : (project_id, doc_id, docLines, version, _callback)->
+	putDocInMemory : (project_id, doc_id, docLines, version, track_changes, track_changes_entries, _callback)->
 		timer = new metrics.Timer("redis.put-doc")
 		callback = (error) ->
 			timer.done()
@@ -23,6 +23,8 @@ module.exports = RedisManager =
 		multi.set keys.docLines(doc_id:doc_id), JSON.stringify(docLines)
 		multi.set keys.projectKey({doc_id:doc_id}), project_id
 		multi.set keys.docVersion(doc_id:doc_id), version
+		multi.set keys.trackChangesEnabled(doc_id:doc_id), if track_changes then "1" else "0"
+		multi.set keys.trackChangesEntries(doc_id:doc_id), JSON.stringify(track_changes_entries)
 		multi.exec (error) ->
 			return callback(error) if error?
 			rclient.sadd keys.docsInProject(project_id:project_id), doc_id, callback
@@ -41,30 +43,36 @@ module.exports = RedisManager =
 		multi.del keys.docLines(doc_id:doc_id)
 		multi.del keys.projectKey(doc_id:doc_id)
 		multi.del keys.docVersion(doc_id:doc_id)
+		multi.del keys.trackChangesEnabled(doc_id:doc_id)
+		multi.del keys.trackChangesEntries(doc_id:doc_id)
 		multi.exec (error) ->
 			return callback(error) if error?
 			rclient.srem keys.docsInProject(project_id:project_id), doc_id, callback
 
-	getDoc : (project_id, doc_id, callback = (error, lines, version, project_id) ->)->
+	getDoc : (project_id, doc_id, callback = (error, lines, version, track_changes, track_changes_entries) ->)->
 		timer = new metrics.Timer("redis.get-doc")
 		multi = rclient.multi()
 		multi.get keys.docLines(doc_id:doc_id)
 		multi.get keys.docVersion(doc_id:doc_id)
 		multi.get keys.projectKey(doc_id:doc_id)
+		multi.get keys.trackChangesEnabled(doc_id:doc_id)
+		multi.get keys.trackChangesEntries(doc_id:doc_id)
 		multi.exec (error, result)->
 			timer.done()
 			return callback(error) if error?
 			try
 				docLines = JSON.parse result[0]
+				track_changes_entries = JSON.parse result[4]
 			catch e
 				return callback(e)
 			version = parseInt(result[1] or 0, 10)
 			doc_project_id = result[2]
+			track_changes = (result[3] == "1")
 			# check doc is in requested project
 			if doc_project_id? and doc_project_id isnt project_id
 				logger.error project_id: project_id, doc_id: doc_id, doc_project_id: doc_project_id, "doc not in project"
 				return callback(new Errors.NotFoundError("document not found"))
-			callback null, docLines, version, project_id
+			callback null, docLines, version, track_changes, track_changes_entries
 
 	getDocVersion: (doc_id, callback = (error, version) ->) ->
 		rclient.get keys.docVersion(doc_id: doc_id), (error, version) ->
@@ -104,7 +112,7 @@ module.exports = RedisManager =
 
 	DOC_OPS_TTL: 60 * minutes
 	DOC_OPS_MAX_LENGTH: 100
-	updateDocument : (doc_id, docLines, newVersion, appliedOps = [], callback = (error) ->)->
+	updateDocument : (doc_id, docLines, newVersion, appliedOps = [], track_changes_entries, callback = (error) ->)->
 		RedisManager.getDocVersion doc_id, (error, currentVersion) ->
 			return callback(error) if error?
 			if currentVersion + appliedOps.length != newVersion
@@ -119,6 +127,7 @@ module.exports = RedisManager =
 				multi.rpush  keys.docOps(doc_id: doc_id), jsonOps...
 			multi.expire keys.docOps(doc_id: doc_id), RedisManager.DOC_OPS_TTL
 			multi.ltrim  keys.docOps(doc_id: doc_id), -RedisManager.DOC_OPS_MAX_LENGTH, -1
+			multi.set    keys.trackChangesEntries(doc_id:doc_id), JSON.stringify(track_changes_entries)
 			multi.exec (error, replys) ->
 					return callback(error) if error?
 					return callback()
@@ -126,3 +135,6 @@ module.exports = RedisManager =
 	getDocIdsInProject: (project_id, callback = (error, doc_ids) ->) ->
 		rclient.smembers keys.docsInProject(project_id: project_id), callback
 
+	setTrackChanges: (project_id, doc_id, track_changes_on, callback = (error) ->) ->
+		value = (if track_changes_on then "1" else "0")
+		rclient.set keys.trackChangesEnabled({doc_id}), value, callback
diff --git a/services/document-updater/app/coffee/ShareJsDB.coffee b/services/document-updater/app/coffee/ShareJsDB.coffee
index 3d80c680cb..a21c8aea7f 100644
--- a/services/document-updater/app/coffee/ShareJsDB.coffee
+++ b/services/document-updater/app/coffee/ShareJsDB.coffee
@@ -1,12 +1,11 @@
 Keys = require('./UpdateKeys')
 Settings = require('settings-sharelatex')
-DocumentManager = require "./DocumentManager"
 RedisManager = require "./RedisManager"
 Errors = require "./Errors"
 logger = require "logger-sharelatex"
 
 module.exports = class ShareJsDB
-	constructor: () ->
+	constructor: (@project_id, @doc_id, @lines, @version) ->
 		@appliedOps = {}
 		# ShareJS calls this detacted from the instance, so we need
 		# bind it to keep our context that can access @appliedOps
@@ -31,22 +30,14 @@ module.exports = class ShareJsDB
 		callback()
 
 	getSnapshot: (doc_key, callback) ->
-		[project_id, doc_id] = Keys.splitProjectIdAndDocId(doc_key)
-		DocumentManager.getDoc project_id, doc_id, (error, lines, version) ->
-			return callback(error) if error?
-			if !lines? or !version?
-				return callback(new Errors.NotFoundError("document not found: #{doc_id}"))
-
-			if lines.length > 0 and lines[0].text?
-				type = "json"
-				snapshot = lines: lines
-			else
-				type = "text"
-				snapshot = lines.join("\n")
-			callback null,
-				snapshot: snapshot
-				v: parseInt(version, 10)
-				type: type
+		if doc_key != Keys.combineProjectIdAndDocId(@project_id, @doc_id)
+			return callback(new Errors.NotFoundError("unexpected doc_key #{doc_key}, expected #{Keys.combineProjectIdAndDocId(@project_id, @doc_id)}"))
+		else
+			return callback null, {
+				snapshot: @lines.join("\n")
+				v: parseInt(@version, 10)
+				type: "text"
+			}
 
 	# To be able to remove a doc from the ShareJS memory
 	# we need to called Model::delete, which calls this 
diff --git a/services/document-updater/app/coffee/ShareJsUpdateManager.coffee b/services/document-updater/app/coffee/ShareJsUpdateManager.coffee
index 985d03094a..876d56e71b 100644
--- a/services/document-updater/app/coffee/ShareJsUpdateManager.coffee
+++ b/services/document-updater/app/coffee/ShareJsUpdateManager.coffee
@@ -6,22 +6,19 @@ Settings = require('settings-sharelatex')
 Keys = require "./UpdateKeys"
 {EventEmitter} = require "events"
 util = require "util"
-
-redis = require("redis-sharelatex")
-rclient = redis.createClient(Settings.redis.web)
-
+WebRedisManager = require "./WebRedisManager"
 
 ShareJsModel:: = {}
 util.inherits ShareJsModel, EventEmitter
 
 module.exports = ShareJsUpdateManager =
-	getNewShareJsModel: () ->
-		db = new ShareJsDB()
+	getNewShareJsModel: (project_id, doc_id, lines, version) ->
+		db = new ShareJsDB(project_id, doc_id, lines, version)
 		model = new ShareJsModel(db, maxDocLength: Settings.max_doc_length)
 		model.db = db
 		return model
 
-	applyUpdate: (project_id, doc_id, update, callback = (error, updatedDocLines) ->) ->
+	applyUpdate: (project_id, doc_id, update, lines, version, callback = (error, updatedDocLines) ->) ->
 		logger.log project_id: project_id, doc_id: doc_id, update: update, "applying sharejs updates"
 		jobs = []
 
@@ -30,7 +27,7 @@ module.exports = ShareJsUpdateManager =
 		# getting stuck due to queued callbacks (line 260 of sharejs/server/model.coffee)
 		# This adds a small but hopefully acceptable overhead (~12ms per 1000 updates on
 		# my 2009 MBP).
-		model = @getNewShareJsModel()
+		model = @getNewShareJsModel(project_id, doc_id, lines, version)
 		@_listenForOps(model)
 		doc_key = Keys.combineProjectIdAndDocId(project_id, doc_id)
 		model.applyOp doc_key, update, (error) ->
@@ -55,18 +52,9 @@ module.exports = ShareJsUpdateManager =
 			[project_id, doc_id] = Keys.splitProjectIdAndDocId(doc_key)
 			ShareJsUpdateManager._sendOp(project_id, doc_id, opData)
 	
-	_sendOp: (project_id, doc_id, opData) ->
-		data =
-			project_id: project_id
-			doc_id: doc_id
-			op: opData
-		data = JSON.stringify data
-		rclient.publish "applied-ops", data
+	_sendOp: (project_id, doc_id, op) ->
+		WebRedisManager.sendData {project_id, doc_id, op}
 
 	_sendError: (project_id, doc_id, error) ->
-		data = JSON.stringify
-			project_id: project_id
-			doc_id: doc_id
-			error: error.message || error
-		rclient.publish "applied-ops", data
+		WebRedisManager.sendData {project_id, doc_id, error: error.message || error}
 		
diff --git a/services/document-updater/app/coffee/TrackChangesManager.coffee b/services/document-updater/app/coffee/TrackChangesManager.coffee
index 9aa1c0ad47..94f8a11ca1 100644
--- a/services/document-updater/app/coffee/TrackChangesManager.coffee
+++ b/services/document-updater/app/coffee/TrackChangesManager.coffee
@@ -1,44 +1,12 @@
-settings = require "settings-sharelatex"
-request  = require "request"
-logger = require "logger-sharelatex"
-async = require "async"
-WebRedisManager = require "./WebRedisManager"
+ChangesTracker = require "./ChangesTracker"
 
 module.exports = TrackChangesManager =
-	flushDocChanges: (project_id, doc_id, callback = (error) ->) ->
-		if !settings.apis?.trackchanges?
-			logger.warn doc_id: doc_id, "track changes API is not configured, so not flushing"
-			return callback()
-
-		url = "#{settings.apis.trackchanges.url}/project/#{project_id}/doc/#{doc_id}/flush"
-		logger.log project_id: project_id, doc_id: doc_id, url: url, "flushing doc in track changes api"
-		request.post url, (error, res, body)->
-			if error?
-				return callback(error)
-			else if res.statusCode >= 200 and res.statusCode < 300
-				return callback(null)
-			else
-				error = new Error("track changes api returned a failure status code: #{res.statusCode}")
-				return callback(error)
-
-	FLUSH_EVERY_N_OPS: 50
-	pushUncompressedHistoryOps: (project_id, doc_id, ops = [], callback = (error) ->) ->
-		if ops.length == 0
-			return callback()
-		WebRedisManager.pushUncompressedHistoryOps project_id, doc_id, ops, (error, length) ->
-			return callback(error) if error?
-			# We want to flush every 50 ops, i.e. 50, 100, 150, etc
-			# Find out which 'block' (i.e. 0-49, 50-99) we were in before and after pushing these
-			# ops. If we've changed, then we've gone over a multiple of 50 and should flush.
-			# (Most of the time, we will only hit 50 and then flushing will put us back to 0)
-			previousLength = length - ops.length
-			prevBlock = Math.floor(previousLength / TrackChangesManager.FLUSH_EVERY_N_OPS)
-			newBlock  = Math.floor(length / TrackChangesManager.FLUSH_EVERY_N_OPS)
-			if newBlock != prevBlock
-				# Do this in the background since it uses HTTP and so may be too
-				# slow to wait for when processing a doc update.
-				logger.log length: length, doc_id: doc_id, project_id: project_id, "flushing track changes api"
-				TrackChangesManager.flushDocChanges project_id, doc_id,  (error) ->
-					if error?
-						logger.error err: error, doc_id: doc_id, project_id: project_id, "error flushing doc to track changes api"
-			callback()
\ No newline at end of file
+	applyUpdate: (project_id, doc_id, entries = {}, updates = [], track_changes, callback = (error, new_entries) ->) ->
+		{changes, comments} = entries
+		changesTracker = new ChangesTracker(changes, comments)
+		changesTracker.track_changes = track_changes
+		for update in updates
+			for op in update.op
+				changesTracker.applyOp(op, { user_id: update.meta?.user_id,  })
+		{changes, comments} = changesTracker
+		callback null, {changes, comments}
\ No newline at end of file
diff --git a/services/document-updater/app/coffee/UpdateManager.coffee b/services/document-updater/app/coffee/UpdateManager.coffee
index f35bc1a9b7..d08d9a62f3 100644
--- a/services/document-updater/app/coffee/UpdateManager.coffee
+++ b/services/document-updater/app/coffee/UpdateManager.coffee
@@ -2,11 +2,14 @@ LockManager = require "./LockManager"
 RedisManager = require "./RedisManager"
 WebRedisManager = require "./WebRedisManager"
 ShareJsUpdateManager = require "./ShareJsUpdateManager"
-TrackChangesManager = require "./TrackChangesManager"
+HistoryManager = require "./HistoryManager"
 Settings = require('settings-sharelatex')
 async = require("async")
 logger = require('logger-sharelatex')
 Metrics = require "./Metrics"
+Errors = require "./Errors"
+DocumentManager = require "./DocumentManager"
+TrackChangesManager = require "./TrackChangesManager"
 
 module.exports = UpdateManager =
 	processOutstandingUpdates: (project_id, doc_id, callback = (error) ->) ->
@@ -45,12 +48,18 @@ module.exports = UpdateManager =
 
 	applyUpdate: (project_id, doc_id, update, callback = (error) ->) ->
 		UpdateManager._sanitizeUpdate update
-		ShareJsUpdateManager.applyUpdate project_id, doc_id, update, (error, updatedDocLines, version, appliedOps) ->
+		DocumentManager.getDoc project_id, doc_id, (error, lines, version, track_changes, track_changes_entries) ->
 			return callback(error) if error?
-			logger.log doc_id: doc_id, version: version, "updating doc in redis"
-			RedisManager.updateDocument doc_id, updatedDocLines, version, appliedOps, (error) ->
+			if !lines? or !version?
+				return callback(new Errors.NotFoundError("document not found: #{doc_id}"))
+			ShareJsUpdateManager.applyUpdate project_id, doc_id, update, lines, version, (error, updatedDocLines, version, appliedOps) ->
 				return callback(error) if error?
-				TrackChangesManager.pushUncompressedHistoryOps project_id, doc_id, appliedOps, callback
+				TrackChangesManager.applyUpdate project_id, doc_id, track_changes_entries, appliedOps, track_changes, (error, new_track_changes_entries) ->
+					return callback(error) if error?
+					logger.log doc_id: doc_id, version: version, "updating doc in redis"
+					RedisManager.updateDocument doc_id, updatedDocLines, version, appliedOps, new_track_changes_entries, (error) ->
+						return callback(error) if error?
+						HistoryManager.pushUncompressedHistoryOps project_id, doc_id, appliedOps, callback
 
 	lockUpdatesAndDo: (method, project_id, doc_id, args..., callback) ->
 		LockManager.getLock doc_id, (error, lockValue) ->
diff --git a/services/document-updater/app/coffee/WebRedisManager.coffee b/services/document-updater/app/coffee/WebRedisManager.coffee
index 73c099f9da..eb3b6a583c 100644
--- a/services/document-updater/app/coffee/WebRedisManager.coffee
+++ b/services/document-updater/app/coffee/WebRedisManager.coffee
@@ -32,4 +32,7 @@ module.exports = WebRedisManager =
 		], (error, results) ->
 			return callback(error) if error?
 			[length, _] = results
-			callback(error, length)
\ No newline at end of file
+			callback(error, length)
+	
+	sendData: (data) ->
+		rclient.publish "applied-ops", JSON.stringify(data)
\ No newline at end of file
diff --git a/services/document-updater/config/settings.defaults.coffee b/services/document-updater/config/settings.defaults.coffee
index 15456db932..edb8c56ad3 100755
--- a/services/document-updater/config/settings.defaults.coffee
+++ b/services/document-updater/config/settings.defaults.coffee
@@ -32,6 +32,8 @@ module.exports =
 				docVersion: ({doc_id}) -> "DocVersion:#{doc_id}"
 				projectKey: ({doc_id}) -> "ProjectId:#{doc_id}"
 				docsInProject: ({project_id}) -> "DocsIn:#{project_id}"
+				trackChangesEnabled: ({doc_id}) -> "TrackChangesEnabled:#{doc_id}"
+				trackChangesEntries: ({doc_id}) -> "TrackChangesEntries:#{doc_id}"
 		# }, {
 		# 	cluster: [{
 		# 		port: "7000"
@@ -44,6 +46,8 @@ module.exports =
 		# 		docVersion: ({doc_id}) -> "DocVersion:{#{doc_id}}"
 		# 		projectKey: ({doc_id}) -> "ProjectId:{#{doc_id}}"
 		# 		docsInProject: ({project_id}) -> "DocsIn:{#{project_id}}"
+		# 		trackChangesEnabled: ({doc_id}) -> "TrackChangesEnabled:{#{doc_id}}"
+		# 		trackChangesEntries: ({doc_id}) -> "TrackChangesEntries:{#{doc_id}}"
 		}]
 	
 	max_doc_length: 2 * 1024 * 1024 # 2mb
diff --git a/services/document-updater/test/acceptance/coffee/TrackChangesTests.coffee b/services/document-updater/test/acceptance/coffee/TrackChangesTests.coffee
new file mode 100644
index 0000000000..406f46b430
--- /dev/null
+++ b/services/document-updater/test/acceptance/coffee/TrackChangesTests.coffee
@@ -0,0 +1,96 @@
+sinon = require "sinon"
+chai = require("chai")
+chai.should()
+async = require "async"
+rclient = require("redis").createClient()
+
+MockWebApi = require "./helpers/MockWebApi"
+DocUpdaterClient = require "./helpers/DocUpdaterClient"
+
+describe "Track changes", ->
+	describe "turning on track changes", ->
+		before (done) ->
+			DocUpdaterClient.subscribeToAppliedOps @appliedOpsListener = sinon.stub()
+			@project_id = DocUpdaterClient.randomId()
+			@docs = [{
+				id: doc_id0 = DocUpdaterClient.randomId()
+				lines: ["one", "two", "three"]
+				updatedLines: ["one", "one and a half", "two", "three"]
+			}, {
+				id: doc_id1 = DocUpdaterClient.randomId()
+				lines: ["four", "five", "six"]
+				updatedLines: ["four", "four and a half", "five", "six"]
+			}]
+			for doc in @docs
+				MockWebApi.insertDoc @project_id, doc.id, {
+					lines: doc.lines
+					version: 0
+				}
+			async.series @docs.map((doc) =>
+				(callback) =>
+					DocUpdaterClient.preloadDoc @project_id, doc.id, callback
+			), (error) =>
+				throw error if error?
+				setTimeout () =>
+					DocUpdaterClient.setTrackChangesOn @project_id, (error, res, body) =>
+						@statusCode = res.statusCode
+						done()
+				, 200
+
+		it "should return a 204 status code", ->
+			@statusCode.should.equal 204
+
+		it "should send a track changes message to real-time for each doc", ->
+			@appliedOpsListener.calledWith("applied-ops", JSON.stringify({
+				project_id: @project_id, doc_id: @docs[0].id, track_changes_on: true
+			})).should.equal true
+			@appliedOpsListener.calledWith("applied-ops", JSON.stringify({
+				project_id: @project_id, doc_id: @docs[1].id, track_changes_on: true
+			})).should.equal true
+		
+		it "should set the track changes key in redis", (done) ->
+			rclient.get "TrackChangesEnabled:#{@docs[0].id}", (error, value) =>
+				throw error if error?
+				value.should.equal "1"
+				rclient.get "TrackChangesEnabled:#{@docs[1].id}", (error, value) ->
+					throw error if error?
+					value.should.equal "1"
+					done()
+	
+	describe "tracking changes", ->
+		before (done) ->
+			@project_id = DocUpdaterClient.randomId()
+			@doc = {
+				id: doc_id0 = DocUpdaterClient.randomId()
+				lines: ["one", "two", "three"]
+			}
+			@update =
+				doc: @doc.id
+				op: [{
+					i: "one and a half\n"
+					p: 4
+				}]
+				v: 0
+				meta:
+					user_id: @user_id = DocUpdaterClient.randomId()
+			MockWebApi.insertDoc @project_id, @doc.id, {
+				lines: @doc.lines
+				version: 0
+			}
+			DocUpdaterClient.preloadDoc @project_id, @doc.id, (error) =>
+				throw error if error?
+				DocUpdaterClient.setTrackChangesOn @project_id, (error, res, body) =>
+					throw error if error?
+					DocUpdaterClient.sendUpdate @project_id, @doc.id, @update, (error) ->
+						throw error if error?
+						setTimeout done, 200
+		
+		it "should set the updated track changes entries in redis", (done) ->
+			rclient.get "TrackChangesEntries:#{@doc.id}", (error, value) =>
+				throw error if error?
+				entries = JSON.parse(value)
+				change = entries.changes[0]
+				change.op.should.deep.equal @update.op[0]
+				change.metadata.user_id.should.equal @user_id
+				done()
+
diff --git a/services/document-updater/test/acceptance/coffee/helpers/DocUpdaterClient.coffee b/services/document-updater/test/acceptance/coffee/helpers/DocUpdaterClient.coffee
index a14f6f9364..b90e7ea82e 100644
--- a/services/document-updater/test/acceptance/coffee/helpers/DocUpdaterClient.coffee
+++ b/services/document-updater/test/acceptance/coffee/helpers/DocUpdaterClient.coffee
@@ -72,7 +72,18 @@ module.exports = DocUpdaterClient =
 
 	deleteProject: (project_id, callback = () ->) ->
 		request.del "http://localhost:3003/project/#{project_id}", callback
-		
-		
-		
-	
+
+	setTrackChangesOn: (project_id, callback = () ->) ->
+		request.post {
+			url: "http://localhost:3003/project/#{project_id}/track_changes"
+			json:
+				on: true
+		}, callback
+
+	setTrackChangesOff: (project_id, callback = () ->) ->
+		request.post {
+			url: "http://localhost:3003/project/#{project_id}/track_changes"
+			json:
+				on: false
+		}, callback
+