Firefox will support non-standard CSS for WebKit compatibility

Plans are afoot for Firefox to work with pre-complete web standards as implemented in rivals’ browsers.

Mozilla developers have revealed a plan to implement support for a subset of non-standard CSS prefixes used in WebKit, –webkit.

Changes are planned for either Firefox 46 or 47, set to be released around April and May.

WebKit is the layout engine employed by Apple’s Safari and forked in Chromium-browsers from Google and Opera. The plan to work with non-Mozilla CSS prefixes seems intended to make Firefox capable of working with both the legacy and the mobile web.

Browser-specific prefixes for standards are a tool that have been employed by browser makers and developers to continue their work with new standards on leading-edge areas while the standards themselves are are being thrashed out.

Prefixes mean that rather than awaiting the outcome of a slow-paced standards process, browser makers and devs can press on with their work. The idea is the prefix is removed upon the standard’s completion.

However, it seems people haven’t bothered to clean house and remove the prefixes upon completion of CSS, at least, leading to the continued existence of browser-specific prefixes across the web.

This is becoming a problem with WebKit thanks to success of Apple’s iOS and of Google’s Chrome. Firefox – which had employed -moz prefixes – has seen its market share eroded.

A post by Mozilla developer Daniel Holbert (here) says:

A good chunk of the web today (and particularly the mobile web) effectively relies on -webkit prefixed CSS properties & features. We wish we lived in a world where web content always included standards-based fallback (or at least multiple-vendor-prefixed fallback), but alas, we do not live in that world.

To be successful at rendering the web as it exists, we need to add support for a list of frequently-used -webkit prefixed CSS properties & features.

In a separate document, here, Mozilla web compatibility specialist Mike Taylor explained:

“There exists an increasingly large corpus of web content that depends on web browsers supporting a number of webkit-prefixed CSS properties and DOM APIs for functionality or layout. This holds especially true for mobile-optimized web content.

"This specification aims to describe the minimal set of webkit-prefixed CSS properties and DOM APIs that user agents are required to support for web compatib.”

Taylor also listed a proposed set of webkit prefixes for Firefox.

This is Mozilla’s latest move to closer workability with Chrome: the WebExtensions API, currently underway, will let extensions written for Chrome run, supposedly unchanged, in Firefox. ®