Firefox is moving towards the WebExtensions standard which promises improvements in stability, cross-browser compatibility, and more security. At the same time they're gradually dropping support for legacy add-ons (bootstrapped extensions, add-on SDK, etc.).
Unfortunately, the WebExtension APIs are much less powerful than legacy add-ons which by contrast have full control over the browser. I fully understand the motivation for the switch, but the features my add-on provides just can't possibly work with limited capabilities of a WebExtension.
What are my options to continue developing a legacy add-on with as few cutbacks as possible? How do other add-ons that won't work as a pure WebExtension solve this problem? Are there any niche projects dedicated to maintaining some sort of legacy extension "hack", or will I have to heavily modify Firefox myself to get any legacy add-ons installed in the future?
(I'm aware that I won't be able to submit my add-on to AMO or get it signed by Mozilla and that supporting full extensions is a potential security risk. But since my add-on is targeting a tech-savvy audience, I'm not too concerned about moderately complex workarounds.)
As the magic 8 ball says: "Cannot predict now".
The reality is that we don't know yet what is going to be required to continue to run non-WebExtensions based add-ons past the release of Firefox 57. All we know is that Mozilla has stated that for Firefox 57:
- Firefox will only run WebExtensions.
- AMO will continue to support listing and updating legacy add-ons after the release of 57 in order to have an easier transition. The exact cut-off time for this support hasn’t been determined yet.
It had previously been stated that the restriction to WebExtensions-only would only apply to the Release and Beta channels, so:
It may be possible to continue to run non-WebExtension based add-ons on:
It is currently unclear if these will actually be possibilities. If they will be possibilities, it is unclear for how long it will remain possible for older add-ons to function (both due to changes to Firefox and/or non-WebExtensions being intentionally disabled). The fact that AMO will continue to support listing and updates to non-WebExtension add-ons is an encouraging sign that we will still be able to use them in Firefox releases that are not the main Release and Beta channels.
Other options include:
You should keep in mind that the plans are for Firefox to fundamentally change in the future. A significant reason for moving away from the more capable add-on types (non-WebExtensions based extensions along with complete-themes) is to allow Firefox to be changed without the need to consider maintaining compatibility with more capable add-ons which rely on the internals of Firefox for their operation. When, exactly, these breaking changes will be rolled out is unclear.
Personally, I'm in a similar boat. None of my released add-ons are possible to move to WebExtensions. Many of the other add-ons which I use are clearly not possible to move to WebExtensions. Frankly, I'm not looking forward to using Firefox without the capabilities some of those add-ons provide. Thus, I will be continuing to look at what options are available as we get closer to Firefox 57.
However, even if I find no option to use more capable add-ons after Firefox 52 ESR is EOL'ed, I may continue to use Firefox. My primary reason for doing so instead of switching to Chrome would be the fact that Firefox extensions go through a review process, whereas Chrome extensions released though the Chrome store can be very bad from the point of view of both security and privacy.