diff --git a/_debug_replacements.php b/_debug_replacements.php
index 520a5ad..190dfbe 100644
--- a/_debug_replacements.php
+++ b/_debug_replacements.php
@@ -8,7 +8,6 @@
 
 $vers = '???';
 $versfn = __DIR__ . '/../user/version.h';
-$myHash = shell_exec('git rev-parse --short HEAD');
 $fwHash = '00000000';
 if (file_exists($versfn)) {
 	$f = file_get_contents($versfn);
@@ -64,7 +63,7 @@ return [
 	'githubrepo' => 'https://github.com/espterm/espterm-firmware',
 	'githubrepo_front' => 'https://github.com/espterm/espterm-front-end',
 	'hash_backend' => $fwHash,
-	'hash_frontend' => $myHash, // TODO actual versions?
+	'hash_frontend' => GIT_HASH, // TODO actual versions?
 
 	'ap_dhcp_time' => '120',
 	'ap_dhcp_start' => '192.168.4.100',
diff --git a/base.php b/base.php
index 717365d..7308e34 100644
--- a/base.php
+++ b/base.php
@@ -16,6 +16,8 @@ if (!file_exists(__DIR__ . '/_env.php')) {
 	die("Copy <b>_env.php.example</b> to <b>_env.php</b> and check the settings inside!");
 }
 
+define('GIT_HASH', trim(shell_exec('git rev-parse --short HEAD')));
+
 require_once __DIR__ . '/_env.php';
 
 $prod = defined('STDIN');
diff --git a/build.sh b/build.sh
index 5bba76b..7f10082 100755
--- a/build.sh
+++ b/build.sh
@@ -2,6 +2,8 @@
 
 cd $(dirname $0)
 
+FRONT_END_HASH=$(git rev-parse --short HEAD)
+
 rm -r out/*
 mkdir out/js
 mkdir out/css
@@ -10,7 +12,7 @@ echo 'Generating lang.js...'
 php ./dump_js_lang.php
 
 echo 'Packing JS...'
-npm run babel -- -o out/js/app.js --source-maps js/lib \
+npm run babel -- -o "out/js/app.$FRONT_END_HASH.js" --source-maps js/lib \
     js/lib/chibi.js \
     js/lib/keymaster.js \
     js/lib/polyfills.js \
@@ -27,7 +29,7 @@ npm run babel -- -o out/js/app.js --source-maps js/lib \
 
 echo 'Building CSS...'
 
-npm run sass -- --output-style compressed sass/app.scss out/css/app.css
+npm run sass -- --output-style compressed sass/app.scss "out/css/app.$FRONT_END_HASH.css"
 
 echo 'Building HTML...'
 
diff --git a/pages/_head.php b/pages/_head.php
index 3a39b02..c8e5098 100644
--- a/pages/_head.php
+++ b/pages/_head.php
@@ -5,8 +5,8 @@
 	<meta http-equiv="X-UA-Compatible" content="IE=edge">
 	<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
 	<title><?= $_GET['PAGE_TITLE'] ?></title>
-	<link href="/css/app.css" rel="stylesheet">
-	<script src="/js/app.js"></script>
+	<link href="/css/app.<?= GIT_HASH ?>.css" rel="stylesheet">
+	<script src="/js/app.<?= GIT_HASH ?>.js"></script>
 	<script>
 		var _root = <?= JS_WEB_ROOT ?>;
 		var _demo = <?= (int)ESP_DEMO ?>;