extension fasterize
The Fasterize browser extension is your essential companion for quickly checking the optimisation status of pages served through Fasterize. In this article, we provide all you need to know on this essential tool.

Télécharger l'extension Firefox

Download the Chrome extension

The new extension provides various tools and information:

  • Optimisation status

The icon colour indicates the page’s optimisation status:

Page served from Fasterize cache or browser cache.

Page optimised.

Page optimisation in progress.

Page cannot be optimised.

Optimisation failed.

Site not integrated with Fasterize.

The red dot indicates that the site is using HTTP/2.

  • Protocol used to serve the page: HTTP/1.1, SPDY/3.1 or HTTP/2.0

  • Toggle switch: switches between optimised and non-optimised versions, allowing you to check that Fasterize does not break anything on the page.

  • Debug section: this is particularly useful for Fasterize teams, e.g. when configuring customer sites. It provides key information when a support ticket is raised with us.

  • X-fstrz field: provides detailed Fasterize optimisation status. Hover over each letter to see details of its precise meaning. A full list is available here (see the Header section).

  • X-unique-id field: this is a reference number, allowing our support team to quickly locate optimisation logs and speed up the process of reproducing any bugs as they occur.

  • fstrz cookie: particularly useful during A/B testing, providing information on whether or not the session is optimised (true: optimised; false: not optimised).

  • fstrz_vary cookie: at our end, Fasterize implements a cache segmentation scheme for cached pages, whereby multiple versions of each cached page are stored depending on the browser, device or in some cases a specific cookie (the cache entry is keyed on the value of the cookie).
    By looking at the “fstrz_vary” cookie, we can determine whether the page is being cached based on a particular segmentation value.

  • The “enable trace” button adds further debug information to the logs.


So now it’s over to you to have a play with this new extension! If you have any feedback, queries or suggestions, then we are relying on you to let us know.
Your feedback will help us improve our tools and features.

Télécharger l'extension Firefox

Download the Chrome extension

This extension is open source!

As we were creating the Firefox extension, we re-wrote the Chrome version to implement the Web Extension standard, which is supported by Chrome, Firefox and Edge. The source code is available from our Github repository.

Key features of the Web Extension rewrite:

  • We have removed browser-specific differences from manifest.json and the Javascript API. To do so, we took advantage of the Mozilla webextension-polyfill project, allowing a unified interface to be used.
  • We have automated the release process. Google hosts our extension on its store. Firefox does not allow this for extensions associated with commercial products. Instead, our Firefox extension may be downloaded from the project’s Github page.

The fundamentals are now in place for the Edge extension. Please feel free to contribute to the extension if you require a port for this browser.