diff --git a/app.js b/app.js
index 1d0d986..c0a14b3 100644
--- a/app.js
+++ b/app.js
@@ -22,9 +22,9 @@ var flash = require('connect-flash')
 var getImageMimeType = require('./lib/utils.js').getImageMimeType
 
 // core
-var config = require('./lib/config.js')
-var logger = require('./lib/logger.js')
-var response = require('./lib/response.js')
+var config = require('./lib/config')
+var logger = require('./lib/logger')
+var response = require('./lib/response')
 var models = require('./lib/models')
 
 // generate front-end constants by template
diff --git a/lib/history.js b/lib/history.js
index ffed3b9..f46ff49 100644
--- a/lib/history.js
+++ b/lib/history.js
@@ -3,9 +3,9 @@
 // external modules
 
 // core
-var config = require('./config.js')
-var logger = require('./logger.js')
-var response = require('./response.js')
+var config = require('./config')
+var logger = require('./logger')
+var response = require('./response')
 var models = require('./models')
 
 // public
diff --git a/lib/models/index.js b/lib/models/index.js
index 95f900b..458d531 100644
--- a/lib/models/index.js
+++ b/lib/models/index.js
@@ -5,8 +5,8 @@ var path = require('path')
 var Sequelize = require('sequelize')
 
 // core
-var config = require('../config.js')
-var logger = require('../logger.js')
+var config = require('../config')
+var logger = require('../logger')
 
 var dbconfig = config.db
 dbconfig.logging = config.debug ? logger.info : false
diff --git a/lib/models/note.js b/lib/models/note.js
index f7c25bd..c0ef137 100644
--- a/lib/models/note.js
+++ b/lib/models/note.js
@@ -15,11 +15,11 @@ var dmp = new DiffMatchPatch()
 var S = require('string')
 
 // core
-var config = require('../config.js')
-var logger = require('../logger.js')
+var config = require('../config')
+var logger = require('../logger')
 
 // ot
-var ot = require('../ot/index.js')
+var ot = require('../ot')
 
 // permission types
 var permissionTypes = ['freely', 'editable', 'limited', 'locked', 'protected', 'private']
diff --git a/lib/models/revision.js b/lib/models/revision.js
index 581e7ea..6f3a746 100644
--- a/lib/models/revision.js
+++ b/lib/models/revision.js
@@ -7,8 +7,8 @@ var childProcess = require('child_process')
 var shortId = require('shortid')
 
 // core
-var config = require('../config.js')
-var logger = require('../logger.js')
+var config = require('../config')
+var logger = require('../logger')
 
 var dmpWorker = createDmpWorker()
 var dmpCallbackCache = {}
diff --git a/lib/models/user.js b/lib/models/user.js
index 042b0d2..14c30bc 100644
--- a/lib/models/user.js
+++ b/lib/models/user.js
@@ -5,8 +5,8 @@ var Sequelize = require('sequelize')
 var scrypt = require('scrypt')
 
 // core
-var logger = require('../logger.js')
-var letterAvatars = require('../letter-avatars.js')
+var logger = require('../logger')
+var letterAvatars = require('../letter-avatars')
 
 module.exports = function (sequelize, DataTypes) {
   var User = sequelize.define('User', {
diff --git a/lib/realtime.js b/lib/realtime.js
index 618fdad..884edbb 100644
--- a/lib/realtime.js
+++ b/lib/realtime.js
@@ -12,13 +12,13 @@ var chance = new Chance()
 var moment = require('moment')
 
 // core
-var config = require('./config.js')
-var logger = require('./logger.js')
-var history = require('./history.js')
+var config = require('./config')
+var logger = require('./logger')
+var history = require('./history')
 var models = require('./models')
 
 // ot
-var ot = require('./ot/index.js')
+var ot = require('./ot')
 
 // public
 var realtime = {
diff --git a/lib/response.js b/lib/response.js
index 13a94bb..1d1db31 100755
--- a/lib/response.js
+++ b/lib/response.js
@@ -10,8 +10,8 @@ var request = require('request')
 var moment = require('moment')
 
 // core
-var config = require('./config.js')
-var logger = require('./logger.js')
+var config = require('./config')
+var logger = require('./logger')
 var models = require('./models')
 
 // public
diff --git a/lib/web/historyRouter.js b/lib/web/historyRouter.js
index 738e409..1b22c23 100644
--- a/lib/web/historyRouter.js
+++ b/lib/web/historyRouter.js
@@ -3,8 +3,7 @@
 const Router = require('express').Router
 
 const {urlencodedParser} = require('./utils')
-const history = require('../history.js')
-
+const history = require('../history')
 const historyRouter = module.exports = Router()
 
 // get history
diff --git a/lib/workers/dmpWorker.js b/lib/workers/dmpWorker.js
index b0ed0f4..60db0a1 100644
--- a/lib/workers/dmpWorker.js
+++ b/lib/workers/dmpWorker.js
@@ -4,8 +4,8 @@ var DiffMatchPatch = require('diff-match-patch')
 var dmp = new DiffMatchPatch()
 
 // core
-var config = require('../config.js')
-var logger = require('../logger.js')
+var config = require('../config')
+var logger = require('../logger')
 
 process.on('message', function (data) {
   if (!data || !data.msg || !data.cacheKey) {