The developers of the popular userscript extension Greasemonkey for Firefox have announced Greasemonkey 4, a new version of the browser extension.
Greasemonkey 4 will be compatible with Firefox 57 as it will be released as a WebExtension. Mozilla plans to drop support for the legacy add-on system of Firefox when Firefox 57 Stable is released.
While there are some options to continue using legacy add-ons in some versions of Firefox, at least for the time being, most of those are of temporary nature.
This means in turn that add-on developers need to port their add-ons so that they remain compatible with Firefox 57 and newer versions of the web browser. Not all add-ons can be ported on the other hand, as the WebExtensions system does not replicate the functionality of Firefox's legacy add-on system completely.
Update: Greasemonkey 4 is now available as a WebExtension on Mozilla AMO.
Greasemonkey is a high profile extension for Firefox. It has over 880k users at the time of writing. The current version of Greasemonkey that is offered on Mozilla AMO is a legacy add-on. This version won't work anymore in Firefox 57 Stable or Beta if Mozilla does not change the schedule.
The developers of Greasemonkey announced on the official project site that Greasemonkey 4 is in the works. This new version of the browser add-on will be fully compatible with Firefox 57. That's good news for users of the add-on, even though alternatives such as Violentmonkey or Tampermonkey are also available and compatible with Firefox 57.
The downside to this is that the move will break compatibility with some userscripts. This change was not enforced on the developers by the new APIs that Mozilla created, but has been a deliberate decision.
As a result, version 4 of Greasemonkey is a nearly complete re-write. Its interface and feature set have been rebuilt in order to best to work with coming Firefox versions. A variety of compromises have been made. We've elected to make a rare backwards incompatible change.
The decision was made to only support userscripts designed to run asynchronously for performance reasons. This breaks compatibility with older scripts.
Greasemonkey 4 is available as an alpha version currently. Compatibility is restricted to Firefox 56 and earlier however, and not the most recent version of Firefox, Firefox 58.
Greasemonkey users will have to cope with another change: version 4 of the add-on won't come with a text editor anymore but relies on an embedded editor instead. This is a restriction of the new WebExtensions system as extensions cannot access the file system anymore.
The next version of Greasemonkey will be compatible with Firefox 57. That's a good thing, even though it means that some scripts won't work anymore in that version unless they are updated by their authors.
Now You: What's your take on the announcement? Do you use userscripts?