Mozilla is ending support for beta versions of Firefox add-ons. Until now, you could find beta or development versions on addons.mozilla.org (also known as AMO). They were a handy way to try new features first, and give developers a hand by reporting problems and giving feedback.
Unfortunately, Mozilla saw a few problems with this – mainly that it wasn't possible to simply switch to the official release version of an add-on. If the developer stopped updating the beta, but carried on updating the main release, you could be stuck using an outdated, potentially buggy or insecure add-on without realising.
If you still want to lend a hand, developers can host beta versions of extensions themselves, but you won't be able to find them through AMO.
The change will happen at some point this month, though Mozilla hasn't given an exact date, so keep an eye on the Mozilla Add-Ons Blog for details.
Shaking up add-ons
With the release of Firefox Quantum last year, Mozilla made a huge change to the way it handles extensions with an eye to improving security.
Instead of giving developers pretty much free rein, it now uses WebExtensions, which are essentially building blocks for creating add-ons. They make it far harder for anyone to develop a malicious browser extension, but this also means that some of Firefox's most powerful extensions are no longer available.