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Combining and Minifying CSS & JS

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Combining and Minifying CSS & JS

The second big feature of Assetic is its ability to combine our CSS or JS into a single file. First, clear your cache and switch over to the prod environment:

php app/console cache:clear --env=prod

Things still look nice. But view the source. Woh! Our 3 CSS files are now one:

<link rel=”stylesheet” href=”/css/8e49901.css?v=5-return-of-the-jedi” />


If your page does not look fine. that’s actually normal! Keep reading about how to dump your assets.

In the dev environment, Symfony keeps our 3 files so we can debug more easily. In prod, it puts them all together.

More Speed: assetic:dump

But when your browser requests this one CSS file, it’s still being executed through a dynamic Symfony route. For production, that’s way too slow. And depending on your setup, it may not even be working in the prod environment.

The secret? The assetic:dump console command. Run it in the prod environment.

php app/console assetic:dump --env=prod

This wrote a physical file to the web/css directory. And when we refresh, the web server loads this file instead of going through Symfony.

When we deploy our application, this command will be part of our deploy process.

Controlling the Output Filename

Assetic gave our CSS file a weird name - 8e49901.css for me, which is just a random name it created. But we can control this by adding an output option to the stylesheets tag:

{# app/Resources/views/base.html.twig #}
{# ... #}

{% stylesheets
    <link rel="stylesheet" href="{{ asset_url }}" />
{% endstylesheets %}

Refresh and look at the source. Woops, nothing changed! I can’t forget to clear my cache when I’m in the prod environment:

php app/console cache:clear --env=prod

Now the link tag points to this exact spot:

<link rel="stylesheet"
    href="/css/built/layout.css?v=5-return-of-the-jedi" />

And of course, if we dump assetic, it writes this file instead of the one with the funny name:

php app/console assetic:dump --env=prod

I also like to put all my built files into css/built and js/built directories. Add both of these to your .gitignore file. There’s no need to commit these - we can build them at any time:

# .gitignore
# ...