One of the reasons I'm still using Chrome instead of Firefox is the wealth of extensions only available on Chrome, including ones I need for work. In the near future, however, it might be easier for Chrome users to switch to Firefox.
Mozilla is changing its extension API for Firefox to a WebExtensions API, which is "largely compatible with the model used by Chrome and Opera," according to the company, so it will be easier for developers to make extensions across multiple browsers. That's a great thing for users who have favorite extensions that only work on one browser platform.
Developers, however, will have to get their current Firefox extensions validated and signed by Mozilla starting with Firefox 41, slated to be released on September 22nd. Mozilla's reassurance to devs:
For our add-on development community, these changes will bring benefits, like greater cross-browser add-on compatibility, but will also require redevelopment of a number of existing add-ons. We’re making a big investment by expanding the team of engineers, add-on reviewers, and evangelists who work on add-ons and support the community that develops them. They will work with the community to improve and finalize the WebExtensions API, and will help developers of unsupported add-ons make the transition to newer APIs and multi-process support.
Although developers might need to tweak their code to make a Chrome extension compatible with Firefox, the new API will make it easier than before for developers to support both Chrome (and Opera, which uses the same codebase) and Firefox:
The strategy announced here necessarily involves a lot of trade-offs. Developers who already support Chrome extensions will benefit since they will have one codebase to support instead of two. Developers of Firefox-only add-ons will have to make changes. Those changes may require considerable development effort up-front, but we feel the end result will be worth that effort for both Firefox’s users and developers.
Personally, I think this is great and am looking forward to giving Firefox another try. The Next Web reports that Firefox 43 will include the new API and will be released on December 15.