diff --git a/background.js b/background.js
index 21df85f296..001d137f37 100644
--- a/background.js
+++ b/background.js
@@ -1,4 +1,5 @@
 /* global chrome */
+'use strict';
 
 chrome.browserAction.onClicked.addListener(function (tab) {
   chrome.storage.sync.set({ 'chrome-app-sync': true });
diff --git a/nightwatch.js b/nightwatch.js
index 7eb31d268c..3bdd1939ce 100644
--- a/nightwatch.js
+++ b/nightwatch.js
@@ -1,4 +1,5 @@
 'use strict'
+
 var TRAVIS_JOB_NUMBER = process.env.TRAVIS_JOB_NUMBER
 
 module.exports = {
diff --git a/src/app.js b/src/app.js
index ece2be273a..0fe694d55f 100644
--- a/src/app.js
+++ b/src/app.js
@@ -1,4 +1,5 @@
 /* global alert, confirm, prompt, Option, Worker */
+'use strict';
 
 var $ = require('jquery');
 var semver = require('semver');
diff --git a/src/app/compiler-worker.js b/src/app/compiler-worker.js
index f6d01d668e..b0f6dc0a86 100644
--- a/src/app/compiler-worker.js
+++ b/src/app/compiler-worker.js
@@ -1,3 +1,5 @@
+'use strict';
+
 var solc = require('solc/wrapper');
 
 var compileJSON = function () { return ''; };
diff --git a/src/app/compiler.js b/src/app/compiler.js
index 900c9ba666..ad1a99a383 100644
--- a/src/app/compiler.js
+++ b/src/app/compiler.js
@@ -1,3 +1,5 @@
+'use strict';
+
 var solc = require('solc/wrapper');
 
 var webworkify = require('webworkify');
diff --git a/src/app/debugger.js b/src/app/debugger.js
index 398bff35dc..a1ba88b3b8 100644
--- a/src/app/debugger.js
+++ b/src/app/debugger.js
@@ -1,3 +1,5 @@
+'use strict';
+
 var remix = require('ethereum-remix');
 var utils = require('./utils');
 var ace = require('brace');
diff --git a/src/app/editor.js b/src/app/editor.js
index 0d06fcc1e9..e698565ee3 100644
--- a/src/app/editor.js
+++ b/src/app/editor.js
@@ -1,4 +1,5 @@
 /* global BALLOT_EXAMPLE, FileReader */
+'use strict';
 
 var utils = require('./utils');
 
diff --git a/src/app/execution-context.js b/src/app/execution-context.js
index fb396164b5..b5d44818d2 100644
--- a/src/app/execution-context.js
+++ b/src/app/execution-context.js
@@ -1,4 +1,5 @@
 /* global confirm */
+'use strict';
 
 var $ = require('jquery');
 var Web3 = require('web3');
diff --git a/src/app/formalVerification.js b/src/app/formalVerification.js
index 0b729db91a..41676d0e44 100644
--- a/src/app/formalVerification.js
+++ b/src/app/formalVerification.js
@@ -1,3 +1,5 @@
+'use strict';
+
 var $ = require('jquery');
 var EventManager = require('../lib/eventManager');
 
diff --git a/src/app/gist-handler.js b/src/app/gist-handler.js
index b69cbac4fc..a706c73dfd 100644
--- a/src/app/gist-handler.js
+++ b/src/app/gist-handler.js
@@ -1,3 +1,5 @@
+'use strict';
+
 // Allowing window to be overriden for testing
 function GistHandler (_window) {
   if (_window === undefined) _window = window;
diff --git a/src/app/query-params.js b/src/app/query-params.js
index 0b11eac34f..d775d4516e 100644
--- a/src/app/query-params.js
+++ b/src/app/query-params.js
@@ -1,3 +1,5 @@
+'use strict';
+
 // Allowing window to be overriden for testing
 function QueryParams (_window) {
   if (_window === undefined) _window = window;
diff --git a/src/app/renderer.js b/src/app/renderer.js
index 021b7bd8c1..db30368fd2 100644
--- a/src/app/renderer.js
+++ b/src/app/renderer.js
@@ -1,3 +1,5 @@
+'use strict';
+
 var $ = require('jquery');
 
 var utils = require('./utils');
diff --git a/src/app/storage.js b/src/app/storage.js
index b2f5503a50..48a3d9d8ab 100644
--- a/src/app/storage.js
+++ b/src/app/storage.js
@@ -1,4 +1,5 @@
 /* global chrome, confirm */
+'use strict';
 
 var utils = require('./utils');
 
diff --git a/src/app/ui-helper.js b/src/app/ui-helper.js
index 0b364b2ee6..95794a8d6c 100644
--- a/src/app/ui-helper.js
+++ b/src/app/ui-helper.js
@@ -1,3 +1,5 @@
+'use strict';
+
 var $ = require('jquery');
 
 module.exports = {
diff --git a/src/app/utils.js b/src/app/utils.js
index 78d58dc5b1..14d025eab6 100644
--- a/src/app/utils.js
+++ b/src/app/utils.js
@@ -1,3 +1,5 @@
+'use strict';
+
 var SOL_CACHE_FILE_PREFIX = 'sol-cache-file-';
 
 function getCacheFilePrefix () {
diff --git a/src/index.js b/src/index.js
index d77b8385d1..c9d00e4526 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1,3 +1,5 @@
+'use strict';
+
 require('es6-shim');
 var app = require('./app.js');
 var $ = require('jquery');
diff --git a/src/lib/eventManager.js b/src/lib/eventManager.js
index 29c096dfd1..16f96c8dc6 100644
--- a/src/lib/eventManager.js
+++ b/src/lib/eventManager.js
@@ -1,4 +1,5 @@
 'use strict';
+
 function eventManager () {
   this.registered = {};
 }
diff --git a/src/universal-dapp.js b/src/universal-dapp.js
index 53f72b9acb..90b539e09d 100644
--- a/src/universal-dapp.js
+++ b/src/universal-dapp.js
@@ -1,4 +1,5 @@
 /* global prompt */
+'use strict';
 
 var $ = require('jquery');
 var ethJSUtil = require('ethereumjs-util');
diff --git a/test-browser/debugger.js b/test-browser/debugger.js
index e3edcd14e8..92b4edd859 100644
--- a/test-browser/debugger.js
+++ b/test-browser/debugger.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = {
   'Debugger Render': function (browser) {
     browser
diff --git a/test-browser/new-file-test.js b/test-browser/new-file-test.js
index d3d08e20f7..1e8e8210ba 100644
--- a/test-browser/new-file-test.js
+++ b/test-browser/new-file-test.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = {
   'New file test': function (browser) {
     browser
diff --git a/test-browser/smoke-test.js b/test-browser/smoke-test.js
index 18b5484b71..9ce6a9742e 100644
--- a/test-browser/smoke-test.js
+++ b/test-browser/smoke-test.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = {
   'Smoke test': function (browser) {
     browser
diff --git a/test/compiler-test.js b/test/compiler-test.js
index 8144f22188..224bf2f701 100644
--- a/test/compiler-test.js
+++ b/test/compiler-test.js
@@ -1,3 +1,5 @@
+'use strict';
+
 var test = require('tape');
 
 var Compiler = require('../src/app/compiler');
diff --git a/test/gist-handler-test.js b/test/gist-handler-test.js
index d260310aac..bd728754cd 100644
--- a/test/gist-handler-test.js
+++ b/test/gist-handler-test.js
@@ -1,3 +1,5 @@
+'use strict';
+
 var test = require('tape');
 
 var GistHandler = require('../src/app/gist-handler');
diff --git a/test/index.js b/test/index.js
index db15b90e82..0339a49fa1 100644
--- a/test/index.js
+++ b/test/index.js
@@ -1,3 +1,5 @@
+'use strict';
+
 require('./compiler-test');
 require('./gist-handler-test');
 require('./query-params-test');
diff --git a/test/query-params-test.js b/test/query-params-test.js
index e3cff5c546..a9187ef7eb 100644
--- a/test/query-params-test.js
+++ b/test/query-params-test.js
@@ -1,3 +1,5 @@
+'use strict';
+
 var test = require('tape');
 
 var QueryParams = require('../src/app/query-params');