The Web Quality Assurance Checklist

Picto thématique

Best practice n° 219 - The server transmits compressed contents to the clients which accept them.

#Server and performances #Development #Ecodesign


  • Improve the speed of the page’s rendering.
  • Reduce bandwidth costs.
  • Reduce the energy impact related to the consultation of the site.


Activate the server's Gzip or Deflate module to compress JavaScript, CSS and HTML resources.


For each page checked:

  • Check the content compression (Gzip) using a dedicated tool.

Be careful to check all of the linked elements (CSS, JS, HTML) and not just the page itself. Formats such as JPEG or PNG images or zip files which are already compressed, for example, should not be recompressed. If

the size before compression of an element is less than 1 kB, it is not necessary to compress it, because the size might increase.