diff --git a/lib/auth.js b/lib/auth.js
index 1addcba6e..67f1e67b2 100644
--- a/lib/auth.js
+++ b/lib/auth.js
@@ -1,8 +1,8 @@
-var Crypto       = require('crypto')
-var jju          = require('jju')
-var Error        = require('http-errors')
-var Logger       = require('./logger')
-var load_plugins = require('./plugin-loader').load_plugins
+const Crypto       = require('crypto')
+const jju          = require('jju')
+const Error        = require('http-errors')
+const Logger       = require('./logger')
+const load_plugins = require('./plugin-loader').load_plugins;
 
 module.exports = Auth
 
diff --git a/lib/config.js b/lib/config.js
index 50377e239..4d558a534 100644
--- a/lib/config.js
+++ b/lib/config.js
@@ -28,7 +28,10 @@ function Config(config) {
   for (var i in config) {
     if (self[i] == null) self[i] = config[i]
   }
-  if (!self.user_agent) self.user_agent = pkgName + '/' + pkgVersion
+
+  if (!self.user_agent) {
+    self.user_agent = `${pkgName}/${pkgVersion}`;
+  }
 
   // some weird shell scripts are valid yaml files parsed as string
   assert.equal(typeof(config), 'object', 'CONFIG: it doesn\'t look like a valid config file')
@@ -50,7 +53,13 @@ function Config(config) {
     }
   }
 
-  var users = {all:true, anonymous:true, 'undefined':true, owner:true, none:true}
+  var users = {
+    all: true,
+    anonymous: true,
+    'undefined': true,
+    owner: true,
+    none: true
+  };
 
   var check_user_or_uplink = function(arg) {
     assert(arg !== 'all' && arg !== 'owner' && arg !== 'anonymous' && arg !== 'undefined' && arg !== 'none', 'CONFIG: reserved user/uplink name: ' + arg)
@@ -64,13 +73,16 @@ function Config(config) {
     assert(Utils.is_object(self[x]), 'CONFIG: bad "'+x+'" value (object expected)')
   })
 
-  for (var i in self.users) check_user_or_uplink(i)
-  for (var i in self.uplinks) check_user_or_uplink(i)
+  for (var i in self.users) {
+    check_user_or_uplink(i);
+  }
+  for (var i in self.uplinks) {
+    check_user_or_uplink(i);
+  }
 
   for (var i in self.users) {
     assert(self.users[i].password, 'CONFIG: no password for user: ' + i)
-    assert(
-      typeof(self.users[i].password) === 'string' &&
+    assert(typeof(self.users[i].password) === 'string' &&
       self.users[i].password.match(/^[a-f0-9]{40}$/)
     , 'CONFIG: wrong password format for user: ' + i + ', sha1 expected')
   }
diff --git a/lib/local-storage.js b/lib/local-storage.js
index 3a7dfd0d3..f41a8a6f5 100644
--- a/lib/local-storage.js
+++ b/lib/local-storage.js
@@ -1,3 +1,5 @@
+"use strict";
+
 var assert     = require('assert')
 var async      = require('async')
 var Crypto     = require('crypto')
@@ -63,14 +65,13 @@ Storage.prototype.add_package = function(name, info, callback) {
 }
 
 Storage.prototype.remove_package = function(name, callback) {
-  var self = this
-  self.logger.info( { name: name }
+  this.logger.info( { name: name }
                   , 'unpublishing @{name} (all)')
 
-  var storage = self.storage(name)
+  var storage = this.storage(name)
   if (!storage) return callback( Error[404]('no such package available') )
 
-  storage.read_json(info_file, function(err, data) {
+  storage.read_json(info_file, (err, data) => {
     if (err) {
       if (err.code === 'ENOENT') {
         return callback( Error[404]('no such package available') )
@@ -78,7 +79,7 @@ Storage.prototype.remove_package = function(name, callback) {
         return callback(err)
       }
     }
-    self._normalize_package(data)
+    this._normalize_package(data)
 
     storage.unlink(info_file, function(err) {
       if (err) return callback(err)
@@ -108,24 +109,23 @@ Storage.prototype.remove_package = function(name, callback) {
 }
 
 Storage.prototype._read_create_package = function(name, callback) {
-  var self = this
-  var storage = self.storage(name)
+  var storage = this.storage(name)
   if (!storage) {
     var data = get_boilerplate(name)
-    self._normalize_package(data)
+    this._normalize_package(data)
     return callback(null, data)
   }
-  storage.read_json(info_file, function(err, data) {
+  storage.read_json(info_file, (err, data) => {
     // TODO: race condition
     if (err) {
       if (err.code === 'ENOENT') {
         // if package doesn't exist, we create it here
         data = get_boilerplate(name)
       } else {
-        return callback(self._internal_error(err, info_file, 'error reading'))
+        return callback(this._internal_error(err, info_file, 'error reading'))
       }
     }
-    self._normalize_package(data)
+    this._normalize_package(data)
     callback(null, data)
   })
 }
@@ -133,8 +133,7 @@ Storage.prototype._read_create_package = function(name, callback) {
 // synchronize remote package info with the local one
 // TODO: readfile called twice
 Storage.prototype.update_versions = function(name, newdata, callback) {
-  var self = this
-  self._read_create_package(name, function(err, data) {
+  this._read_create_package(name, (err, data) => {
     if (err) return callback(err)
 
     var change = false
@@ -164,7 +163,7 @@ Storage.prototype.update_versions = function(name, newdata, callback) {
               //
               // see https://github.com/rlidwka/sinopia/issues/166
               var tarball_url = URL.parse(hash.url)
-              var uplink_url  = URL.parse(self.config.uplinks[verdata._verdaccio_uplink].url)
+              var uplink_url  = URL.parse(this.config.uplinks[verdata._verdaccio_uplink].url)
               if (uplink_url.host === tarball_url.host) {
                 tarball_url.protocol = uplink_url.protocol
                 hash.registry = verdata._verdaccio_uplink
@@ -197,8 +196,8 @@ Storage.prototype.update_versions = function(name, newdata, callback) {
     }
 
     if (change) {
-      self.logger.debug('updating package info')
-      self._write_package(name, data, function(err) {
+      this.logger.debug('updating package info')
+      this._write_package(name, data, function(err) {
         callback(err, data)
       })
     } else {
@@ -208,8 +207,7 @@ Storage.prototype.update_versions = function(name, newdata, callback) {
 }
 
 Storage.prototype.add_version = function(name, version, metadata, tag, callback) {
-  var self = this
-  self.update_package(name, function updater(data, cb) {
+  this.update_package(name, (data, cb) => {
     // keep only one readme per package
     data.readme = metadata.readme
     delete metadata.readme
@@ -236,16 +234,14 @@ Storage.prototype.add_version = function(name, version, metadata, tag, callback)
 
     data.versions[version] = metadata
     Utils.tag_version(data, version, tag)
-    self.config.localList.add(name)
+    this.config.localList.add(name)
     cb()
   }, callback)
 }
 
 Storage.prototype.merge_tags = function(name, tags, callback) {
-  var self = this
-
-  self.update_package(name, function updater(data, cb) {
-    for (var t in tags) {
+  this.update_package(name, function updater(data, cb) {
+    for (let t in tags) {
       if (tags[t] === null) {
         delete data['dist-tags'][t]
         continue
@@ -262,12 +258,10 @@ Storage.prototype.merge_tags = function(name, tags, callback) {
 }
 
 Storage.prototype.replace_tags = function(name, tags, callback) {
-  var self = this
-
-  self.update_package(name, function updater(data, cb) {
+  this.update_package(name, function updater(data, cb) {
     data['dist-tags'] = {}
 
-    for (var t in tags) {
+    for (let t in tags) {
       if (tags[t] === null) {
         delete data['dist-tags'][t]
         continue
@@ -285,16 +279,15 @@ Storage.prototype.replace_tags = function(name, tags, callback) {
 
 // currently supports unpublishing only
 Storage.prototype.change_package = function(name, metadata, revision, callback) {
-  var self = this
 
   if (!Utils.is_object(metadata.versions) || !Utils.is_object(metadata['dist-tags'])) {
     return callback( Error[422]('bad data') )
   }
 
-  self.update_package(name, function updater(data, cb) {
-    for (var ver in data.versions) {
+  this.update_package(name, (data, cb) => {
+    for (let ver in data.versions) {
       if (metadata.versions[ver] == null) {
-        self.logger.info( { name: name, version: ver }
+        this.logger.info( { name: name, version: ver }
                         , 'unpublishing @{name}@@{version}')
         delete data.versions[ver]
 
@@ -315,9 +308,8 @@ Storage.prototype.change_package = function(name, metadata, revision, callback)
 
 Storage.prototype.remove_tarball = function(name, filename, revision, callback) {
   assert(Utils.validate_name(filename))
-  var self = this
 
-  self.update_package(name, function updater(data, cb) {
+  this.update_package(name, (data, cb) => {
     if (data._attachments[filename]) {
       delete data._attachments[filename]
       cb()
@@ -326,7 +318,7 @@ Storage.prototype.remove_tarball = function(name, filename, revision, callback)
     }
   }, function(err) {
     if (err) return callback(err)
-    var storage = self.storage(name)
+    var storage = this.storage(name)
     if (storage) storage.unlink(filename, callback)
   })
 }
@@ -347,7 +339,6 @@ Storage.prototype.add_tarball = function(name, filename) {
     _transform.apply(stream, arguments)
   }
 
-  var self = this
   if (name === info_file || name === '__proto__') {
     process.nextTick(function() {
       stream.emit('error', Error[403]("can't use this filename"))
@@ -355,7 +346,7 @@ Storage.prototype.add_tarball = function(name, filename) {
     return stream
   }
 
-  var storage = self.storage(name)
+  var storage = this.storage(name)
   if (!storage) {
     process.nextTick(function() {
       stream.emit('error', Error[404]("can't upload this package"))
@@ -365,12 +356,12 @@ Storage.prototype.add_tarball = function(name, filename) {
 
   var wstream = storage.write_stream(filename)
 
-  wstream.on('error', function(err) {
+  wstream.on('error', (err) => {
     if (err.code === 'EEXISTS') {
       stream.emit('error', Error[409]('this tarball is already present'))
     } else if (err.code === 'ENOENT') {
       // check if package exists to throw an appropriate message
-      self.get_package(name, function(_err, res) {
+      this.get_package(name, function(_err, res) {
         if (_err) {
           stream.emit('error', _err)
         } else {
@@ -386,8 +377,8 @@ Storage.prototype.add_tarball = function(name, filename) {
     // re-emitting open because it's handled in storage.js
     stream.emit('open')
   })
-  wstream.on('success', function() {
-    self.update_package(name, function updater(data, cb) {
+  wstream.on('success', () => {
+    this.update_package(name, function updater(data, cb) {
       data._attachments[filename] = {
         shasum: shasum.digest('hex'),
       }
@@ -453,41 +444,41 @@ Storage.prototype.get_tarball = function(name, filename, callback) {
 }
 
 Storage.prototype.get_package = function(name, options, callback) {
-  if (typeof(options) === 'function') callback = options, options = {}
+  if (typeof(options) === 'function') {
+     callback = options, options = {};
+  }
 
-  var self = this
-  var storage = self.storage(name)
+  var storage = this.storage(name)
   if (!storage) return callback( Error[404]('no such package available') )
 
-  storage.read_json(info_file, function(err, result) {
+  storage.read_json(info_file, (err, result) => {
     if (err) {
       if (err.code === 'ENOENT') {
         return callback( Error[404]('no such package available') )
       } else {
-        return callback(self._internal_error(err, info_file, 'error reading'))
+        return callback(this._internal_error(err, info_file, 'error reading'))
       }
     }
-    self._normalize_package(result)
+    this._normalize_package(result)
     callback(err, result)
   })
 }
 
 // walks through each package and calls `on_package` on them
 Storage.prototype._each_package = function (on_package, on_end) {
-  var self = this
   var storages = {}
 
-  storages[self.config.storage] = true
+  storages[this.config.storage] = true;
 
-  if (self.config.packages) {
-    Object.keys(self.packages || {}).map(function (pkg) {
-      if (self.config.packages[pkg].storage) {
-        storages[self.config.packages[pkg].storage] = true
+  if (this.config.packages) {
+    Object.keys(this.packages || {}).map( pkg => {
+      if (this.config.packages[pkg].storage) {
+        storages[this.config.packages[pkg].storage] = true
       }
     })
   }
 
-  var base = Path.dirname(self.config.self_path);
+  const base = Path.dirname(this.config.self_path);
 
   async.eachSeries(Object.keys(storages), function (storage, cb) {
     fs.readdir(Path.resolve(base, storage), function (err, files) {
@@ -502,7 +493,7 @@ Storage.prototype._each_package = function (on_package, on_end) {
             async.eachSeries(files, function (file2, cb) {
               if (Utils.validate_name(file2)) {
                 on_package({
-                  name: file + '/' + file2,
+                  name: `${file}/${file2}`,
                   path: Path.resolve(base, storage, file, file2),
                 }, cb)
               } else {
@@ -583,16 +574,14 @@ Storage.prototype.update_package = function(name, updateFn, _callback) {
 }
 
 Storage.prototype.search = function(startkey, options) {
-  var self = this
-
   var stream = new Stream.PassThrough({ objectMode: true })
 
-  self._each_package(function on_package(item, cb) {
-    fs.stat(item.path, function(err, stats) {
+  this._each_package((item, cb) => {
+    fs.stat(item.path, (err, stats) => {
       if (err) return cb(err)
 
       if (stats.mtime > startkey) {
-        self.get_package(item.name, options, function(err, data) {
+        this.get_package(item.name, options, function(err, data) {
           if (err) return cb(err)
 
           var versions = Utils.semver_sort(Object.keys(data.versions))
@@ -635,8 +624,9 @@ Storage.prototype._normalize_package = function(pkg) {
   ;['versions', 'dist-tags', '_distfiles', '_attachments', '_uplinks'].forEach(function(key) {
     if (!Utils.is_object(pkg[key])) pkg[key] = {}
   })
-  if (typeof(pkg._rev) !== 'string') pkg._rev = '0-0000000000000000'
-
+  if (typeof(pkg._rev) !== 'string') {
+    pkg._rev = '0-0000000000000000';
+  }
   // normalize dist-tags
   Utils.normalize_dist_tags(pkg)
 }
@@ -644,7 +634,9 @@ Storage.prototype._normalize_package = function(pkg) {
 Storage.prototype._write_package = function(name, json, callback) {
 
   // calculate revision a la couchdb
-  if (typeof(json._rev) !== 'string') json._rev = '0-0000000000000000'
+  if (typeof(json._rev) !== 'string') {
+     json._rev = '0-0000000000000000';
+  }
   var rev = json._rev.split('-')
   json._rev = ((+rev[0] || 0) + 1) + '-' + Crypto.pseudoRandomBytes(8).toString('hex')
 
@@ -653,18 +645,18 @@ Storage.prototype._write_package = function(name, json, callback) {
   storage.write_json(info_file, json, callback)
 }
 
-Storage.prototype.storage = function(package) {
-  var path = this.config.get_package_spec(package).storage
+Storage.prototype.storage = function(pkg) {
+  var path = this.config.get_package_spec(pkg).storage
   if (path == null) path = this.config.storage
   if (path == null || path === false) {
-    this.logger.debug( { name: package }
+    this.logger.debug( { name: pkg }
                      , 'this package has no storage defined: @{name}' )
     return null
   }
   return Path_Wrapper(
     Path.join(
       Path.resolve(Path.dirname(this.config.self_path || ''), path),
-      package
+      pkg
     )
   )
 }
diff --git a/lib/plugin-loader.js b/lib/plugin-loader.js
index 17d84203c..c12ea036e 100644
--- a/lib/plugin-loader.js
+++ b/lib/plugin-loader.js
@@ -20,10 +20,10 @@ function load_plugins(config, plugin_configs, params, sanity_check) {
 
     // npm package
     if (plugin === null && p.match(/^[^\.\/]/)) {
-      plugin = try_load('verdaccio-' + p)
+      plugin = try_load(`verdaccio-${p}`)
       // compatibility for old sinopia plugins
       if(!plugin) {
-        plugin = try_load('sinopia-' + p)
+        plugin = try_load(`sinopia-${p}`)
       }
     }
 
diff --git a/lib/status-cats.js b/lib/status-cats.js
index 5c0016a86..df328d02b 100644
--- a/lib/status-cats.js
+++ b/lib/status-cats.js
@@ -1,7 +1,7 @@
 
 // see https://secure.flickr.com/photos/girliemac/sets/72157628409467125
 
-var images = {
+const images = {
   100: 'aVvDhR', // '6512768893', // 100 - Continue
   101: 'aXXExP', // '6540479029', // 101 - Switching Protocols
   200: 'aVuVsF', // '6512628175', // 200 - OK
diff --git a/lib/storage.js b/lib/storage.js
index 823bd5281..5abd84ebf 100644
--- a/lib/storage.js
+++ b/lib/storage.js
@@ -1,3 +1,5 @@
+"use strict";
+
 var assert    = require('assert')
 var async     = require('async')
 var Error     = require('http-errors')
diff --git a/lib/up-storage.js b/lib/up-storage.js
index 8f7606d4d..b94863165 100644
--- a/lib/up-storage.js
+++ b/lib/up-storage.js
@@ -1,3 +1,5 @@
+"use strict";
+
 var JSONStream     = require('JSONStream')
 var Error          = require('http-errors')
 var request        = require('request')
@@ -68,12 +70,14 @@ function _setupProxy(hostname, config, mainconfig, isHTTPS) {
   }
 
   // use wget-like algorithm to determine if proxy shouldn't be used
-  if (hostname[0] !== '.') hostname = '.' + hostname
+  if (hostname[0] !== '.') {
+    hostname = '.' + hostname;
+  }
   if (typeof(no_proxy) === 'string' && no_proxy.length) {
     no_proxy = no_proxy.split(',')
   }
   if (Array.isArray(no_proxy)) {
-    for (var i=0; i<no_proxy.length; i++) {
+    for (let i=0; i<no_proxy.length; i++) {
       var no_proxy_item = no_proxy[i]
       if (no_proxy_item[0] !== '.') no_proxy_item = '.' + no_proxy_item
       if (hostname.lastIndexOf(no_proxy_item) === hostname.length - no_proxy_item.length) {
@@ -82,7 +86,7 @@ function _setupProxy(hostname, config, mainconfig, isHTTPS) {
             'not using proxy for @{url}, excluded by @{rule} rule')
           this.proxy = false
         }
-        break
+        break;
       }
     }
   }
@@ -117,7 +121,7 @@ Storage.prototype.request = function(options, cb) {
   this._add_proxy_headers(options.req, headers)
 
   // add/override headers specified in the config
-  for (var key in this.config.headers) {
+  for (let key in this.config.headers) {
     headers[key] = this.config.headers[key]
   }
 
diff --git a/lib/utils.js b/lib/utils.js
index f342f5816..f2f4696a9 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -52,7 +52,7 @@ module.exports.validate_metadata = function(object, name) {
     object['versions'] = {}
   }
 
-  return object
+  return object;
 }
 
 module.exports.filter_tarball_urls = function(pkg, req, config) {
@@ -67,7 +67,7 @@ module.exports.filter_tarball_urls = function(pkg, req, config) {
       var result = req.protocol + '://' + req.headers.host
     }
 
-    return result + '/' + pkg.name.replace(/\//g, '%2f') + '/-/' + filename
+    return `${result}/${pkg.name.replace(/\//g, '%2f')}/-/${filename}`;
   }
 
   for (var ver in pkg.versions) {