Introduction
This is small tutorial that covers some tips how you can improve the performance of your website. Many of these steps include tasks that can be handled by a build tool (I use Grunt) so I recommend you using a build tool like that. You can test your sites current performance by using a tool like this one or this one.
Don’t use images when it’s not needed
In the earlier days of web development images were used for all sorts of things; buttons, icons, gradients, backgrounds and even texts for displaying headings and logotypes that required specific fonts. With modern day web technlogies though you can easily recreate all of these things without the use of image files.
- Buttons: CSS3 introduced lots of interesting attributes that can create effects that could previously only could be achieved by rendering a image in for instance Photoshop and then using the img-tag. Attributes like border-radius for rounded corners, box-shadow for drop shadow effects, text-shadow for text shadow effects, text-stroke for text outline as well as a bunch of neat CSS animations for click/hover/focus events. You can use a library like Bootstrap to get some decent looking default buttons. Here is a nice codepen as an example of what can be achieved with HTML and CSS only.
- Icons: Instead of using images for small icons consider using a glyph icon library like Bootstrap icons or Fotn awesome. It’s better for performance and also scales better.
- Gradients: If for whatever reason you wan’t to use gradients you can use a gradient css generator like this one to generate css gradients.
- Backgrounds: It is possible to create a lot of quite impressive background patterns using CSS only, here are a few examples of these.
- Texts: With CSS3 you can use custom fonts for texts, so there is no need to create images for headings and logos. Here is a nice tutorial about this. You may also consider using a convenient service like Google fonts for this. Here are a few examples of impressive typographies created using CSS only; Example 1, Example 2, Example 3, Example 4, Example 5, Example 6, Example 7, Example 8
Optimize images
There are obviously still some instances where you must use images, for instance when using photos for hero components and whatnot. When using image files you should remember to optmizie them. You can do this by using a simple service like Optimizilla. You’ll be surprised how much space you can save by optmizing images while not seemingly losing any photo quality at all.
Minify JS
I use the build tool Grunt and the plugin uglify to minify, compress and uglify all my Javascript code. This will reduce the file size making it load faster. Here’s how to set it up using Grunt. First install the plugin (this assumes you already have npm and Grunt setup):
npm install grunt-contrib-uglify --save-dev
Now configure your Gruntfile.js:
module.exports = function(grunt) {
grunt.initConfig({
pkg: grunt.file.readJSON('package.json'),
uglify: {
options: {
banner: '/*! My compressed and uglified JS | <%= grunt.template.today("yyyy-mm-dd") %> */\n'
},
build: {
files: [{
src: 'js/**/*.js',
dest: 'build/main.min.js'
}]
}
}
});
grunt.loadNpmTasks('grunt-contrib-uglify');
grunt.registerTask('default', [
'uglify'
]);
};
Now you can compress and uglify your Javascript by just running the default Grunt build task. This will take all js-files (recursively) in your js-folder and compile them into one large js-file. The output will be located in build/main.min.js.
Minify CSS
Minifying CSS is also recommended. I recommend the Grunt plugin grunt-contrib-cssmin. Install it by running:
npm install grunt-contrib-cssmin --save-dev
Personally I don’t use this plugin. Instead I am using the plugin “grunt-contrib-less” (since I am using less as a css postprocessor). This plugin will not only transpile less to css but also minify. However if you are not using less you can use grunt-contrib-cssmin. I add the following configuration to my Gruntfile.js:
module.exports = function(grunt) {
grunt.initConfig({
pkg: grunt.file.readJSON('package.json'),
uglify: {
options: {
banner: '/*! My compressed and uglified JS | <%= grunt.template.today("yyyy-mm-dd") %> */\n'
},
build: {
files: [{
src: 'js/**/*.js',
dest: 'build/main.min.js'
}]
}
},
cssmin: {
minify: {
src: 'css/default.css',
dest: 'build/default.min.css'
}
}
});
grunt.loadNpmTasks('grunt-contrib-uglify');
grunt.loadNpmTasks('grunt-contrib-cssmin');
grunt.registerTask('default', [
'uglify',
'cssmin'
]);
};
This will take the file css/default.css and minify it, the output will be located in build/default.min.css.
Lazy load CSS
If your website uses very large CSS-files you might wan’t to consider lazy loading your CSS. Or perhaps you could break up your css into a default stylesheet file that can be included normally and one that can be lazyloaded. Simply lazy load css by using the following script:
<script>
var cb = function() {
var l = document.createElement('link');
l.rel = 'stylesheet';
l.href = 'yourCSSfile.css';
var h = document.getElementsByTagName('head')[0];
h.parentNode.insertBefore(l, h);
};
var raf = requestAnimationFrame || mozRequestAnimationFrame ||
webkitRequestAnimationFrame || msRequestAnimationFrame;
if (raf) raf(cb);
else window.addEventListener('load', cb);
</script>
Inline CSS
Another way to speed up your site is to simply inline you CSS. This means that instead of referencing a separate css-file you paste the full css in a style-tag within the head-tag. By doing this your browser won’t have to download the css-file and it reduces the amount of HTTP requests your browser have to make. Obviously it’s not very convenient having to constantly copypaste your css to your markup so I suggest using the grunt plugin grunt-replace for inlining CSS on every build. Simply run:
npm grunt-replace --save-dev
Then modify your Gruntfile.js file so that it looks a bit like this:
module.exports = function(grunt) {
grunt.initConfig({
pkg: grunt.file.readJSON('package.json'),
uglify: {
options: {
banner: '/*! My compressed and uglified JS | <%= grunt.template.today("yyyy-mm-dd") %> */\n'
},
build: {
files: [{
src: 'js/**/*.js',
dest: 'build/main.min.js'
}]
}
},
cssmin: {
minify: {
src: 'css/default.css',
dest: 'build/default.min.css'
}
},
replace: {
inline: {
options: {
patterns: [{
match: 'defaultCss',
replacement: '<%= grunt.file.read("build/default.min.css") %>'
}]
},
files: [{
src: ['head.html'],
dest: 'build/head.html'
}]
}
}
});
grunt.loadNpmTasks('grunt-contrib-uglify');
grunt.loadNpmTasks('grunt-contrib-cssmin');
grunt.loadNpmTasks('grunt-replace');
grunt.registerTask('default', [
'uglify',
'cssmin',
'replace'
]);
};
In your markup instead of referencing the CSS-file normally instead write:
<style>
@@defaultCss
</style>
Now everytime you run the default Grunt build command (by simply executing ‘grunt’ in your terminal) the placeholder variable ‘@@defaultCss’ in head.html will be replaced with the contents of your default.min.css file (in this case located in build/css/). The output file will be located in build/head.html. Note how I am here using the plugins cssmin and replace together. It’s therefore important to run cssmin BEFORE replace as it is cssmin that will generate the minified CSS output.
Server cache of static files
The Apache configuration
Make it so that static files (javascript, css and images) are cached for a longer duration so that they don’t have be fetched from the server on every new page request. This one is a bit trickier as it requires some server configuration (I am using Apache) and you may not have access to the server depending on what webhost you are using, if any. Regardless, this is my fix.
First you must enable the Apache mod “expires” by running:
a2enmod expires
Now restart your server for the change to take effect.
/etc/init.d/apache2 restart
Now that the expires mod is enabled I can configure my settings for the mod by adding it to my .htaccess file in my site root folder.
<IfModule mod_expires.c>
ExpiresActive On
ExpiresDefault "access plus 1 month"
ExpiresByType image/jpg "access 1 year"
ExpiresByType image/jpeg "access 1 year"
ExpiresByType image/gif "access 1 year"
ExpiresByType image/png "access 1 year"
ExpiresByType text/css "access 1 month"
ExpiresByType text/x-javascript "access 1 month"
</IfModule>
You can use whatever expiration time you like, learn more about this mod here.
Naturally there’s an obvious problem with this, what if we make changes to static files which we most certainly will if we regularly update the site? There’s a solution to this which once again involves Grunt.
Grunt job for version-tagging static files
Now I will install the Grunt plugins grunt-filerev, grunt-filerev-replace, grunt-contrib-clean and grunt-contrib-copy. Run:
npm install grunt-filerev grunt-filerev-replace grunt-contrib-copy grunt-contrib-clean --save-dev
Now modify your Gruntfile a bit like this:
module.exports = function(grunt) {
grunt.initConfig({
pkg: grunt.file.readJSON('package.json'),
uglify: {
options: {
banner: '/*! My compressed and uglified JS | <%= grunt.template.today("yyyy-mm-dd") %> */\n'
},
build: {
files: [{
src: 'js/**/*.js',
dest: 'build/main.min.js'
}]
}
},
cssmin: {
minify: {
src: 'css/default.css',
dest: 'build/default.min.css'
}
},
replace: {
inline: {
options: {
patterns: [{
match: 'defaultCss',
replacement: '<%= grunt.file.read("build/default.min.css") %>'
}]
},
files: [{
src: ['build/head.html'],
dest: 'build/head.html'
}]
}
},
filerev: {
options: {
algorithm: 'md5',
length: 8
},
images: {
src: 'build/**/*.{jpg,jpeg,gif,png}'
},
js: {
src: ['build/main.min.js']
}
},
filerev_replace: {
options: {
assets_root: './'
},
compiled_assets: {
src: [
'build/main.min.js',
'build/default.min.css',
'build/head.html'
]
}
},
copy: {
main: {
files: [{
src: 'img/*',
dest: 'build/',
expand: true,
flatten: true
}, {
src: 'head.html',
dest: 'build/head.html'
}]
},
},
clean: {
files: ['build/*']
}
});
grunt.loadNpmTasks('grunt-contrib-uglify');
grunt.loadNpmTasks('grunt-contrib-cssmin');
grunt.loadNpmTasks('grunt-replace');
grunt.loadNpmTasks('grunt-contrib-copy');
grunt.loadNpmTasks('grunt-filerev');
grunt.loadNpmTasks('grunt-filerev-replace');
grunt.loadNpmTasks('grunt-contrib-clean');
grunt.registerTask('default', [
'clean',
'copy',
'uglify',
'filerev',
'cssmin',
'filerev_replace',
'replace'
]);
};
The grunt plugin “filerev” will generate new files from the files specified, in this scenario image files and our js-file (main.min.js), however an MD5 hash will be generated based on the content of the file and appended to the file name. For instance a file named background.png would become background.86182fa8.png. If the files are changed the generated hash that is appended to the filename will also change. This means that everytime a file, for instance the compiled js-file is changed, it will no longer be cached on the server since the filename is changed and thus interpreted as a new file. By using this we can safely cache static files on the server.
The plugin “filerev_replace” will go through the specified files (main.min.js and default.min.css) and replace all references to the original files (like background.png) and change it to the newly generated hashed files (like background.86182fa8.png).
I also added the plugins clean and copy for cleaning previously generated build files and also copying files to be hashed to the build-folder. Here is a full explanation of the flow of tasks:
- clean: Remove all previously built files from the build-folder before doing anything else.
- copy: Copy all images from the img-folder to the build-folder. The reason is that we will later use filerev for the images in the build folder to generate hashed version but we want to let the original images remain. It is the hashed files in the build-folder that will be used, so references to images in css- and js-files should reference for instance build/background.png. The filerev_replace will then modify these references to build/background.86182fa8.png. We also copy the head.html file (this is a file that contains all tags in the head-tag, this file can then be included in the index.html file).
- uglify: Minify, uglify and compress all js files from the js-folder and compile it into one js-file, build/main.min.js.
- filerev: Generate hashed versions of all the images in the build folder and our js-file, build/main.min.js.
- cssmin: Compress and minify css, output will be located in build/default.min.css.
- filerev_replace:: Replace all references to images in main.min.js and default.min.css. As you can see build/head.html is also included, this is because it includes the reference to main.min.js which will be hashed.
- replace: Replace the @@defaultCss placeholder variable in build/head.html and replace it with the content of the default.min.css file. This will inline the css. This is the reason we didn’t include css in the filerev task, because the css is inlined in the markup in this step anyway, it will not be a separate file that the server has to request.
This is about the same Grunt configuration I use on my site and I’m pretty happy with it. I managed to improve the performance of the site a lot by setting this up.
Testing server caching
To test that the files specified in the Apache configuration are now cached properly you can download and install the plugin Live HTTP Headers for Chrome or the Firefox version. Start the plugin and enter your site, watch the server file requests in the Live HTTP Headers plugin and you should now be able to see that image-files and js-files now have an Expires-header and a Cache-Control-header.
Asynchronus js-files
The async-attribute is a new addition to HTML5 and it’s an easy solution to load external javascript-files asynchronously. Note that this is not supported by older browsers like (IE8). Here’s how it looks:
<script async src="build/main.min.js"></script>
The end!
I hope you enjoyed this tutorial. There are more things I could mention regarding website performance but I think I covered the essentials, perhaps one day I will write a part 2 to this tutorial. 🙂
Martin Sonesson 