Fluff Busting Purity

Fluff Busting Purity, or FB Purity for short (previously known as Facebook Purity) is a web browser extension designed to customize the Facebook website's user interface and add extra functionality. Developed by Steve Fernandez, a UK-based programmer, it was first released in 2009 as a Greasemonkey script, as donationware. It is available for Firefox, Google Chrome, Microsoft Edge, Safari, Opera, Brave and Maxthon.

In February 2012, Fernandez was banned from Facebook, although he was allowed back two weeks later. In April, Facebook blocked links to his site, with an error message saying the site was "spammy or abusive", a generic error message given for any site that they deem to have violated their terms and conditions for any reason. Facebook stopped blocking the link to the FB Purity website at some point in 2021, the exact date unknown.

In December 2012, the company both objected to the name "Facebook Purity" (which Fernandez changed to 'Fluff Busting Purity' in response), and claimed that its development violates the site's Terms of Service. In response to this perceived violation, the company told Fernandez he was unauthorized to access Facebook, which he described at the time as potentially the "end of the road" for the script's development. However, the add-on continues to be maintained and updated by the author, which is clear from the regular version releases on the FB Purity website, and other official browser-specific download pages of the FB Purity extension: (Firefox, Google Chrome, Microsoft Edge, Opera ).

During the summer of 2020, Facebook informed users that a new user interface featuring light and dark views would become mandatory, with users temporarily being able to switch back to the Classic look. In response, F.B. Purity v30.6.5 was released, offering an option to retain the older look.