Extensions may be coming to Microsoft's Edge desktop browser sooner than we think. For a brief period, a Microsoft-hosted webpage showing two extensions appears to accidentally have been made public. The page has since been pulled and now displays an Error 403 message.
The two example extensions on the page that appear to be ready for the launch, are for Pinterest and 'RES', the Reddit Enhancement Suite, a collection of enhancements for the site.
Edge extensions will be able to be ported from Chrome with only minor changes using simple tools. @WalkingCat, the Twitter user who discovered the page, scoped through the two extensions revealing this to be the case.
Comparing Edge version vs. Chrome version of same extension, basically substitute "chrome" with "msBrowser", add few minor changes, done.— WalkingCat (@h0x0d) December 10, 2015
Extension support was due to arrive with the November update, but shortly before its release Microsoft announced its delay until 2016. Whenever extensions do arrive, Windows Insiders are expected to be able to test the feature before it is made available to the general public.