Tipsters have been telling a bunch of us Microsoft watchers that the next test version of Windows 10 "Redstone" for PCs would include the first test version of extensions for Microsoft's Edge browser.
Thanks to MSPowerUser.com, the likely launch page for those extensions is now visible (at least for a while until Microsoft likely takes it down).
Microsoft originally had been hoping to get the first Edge extensions in preview form to testers before the end of calendar 2015. Microsoft decided to delay Edge extension support until 2016. Extensions are desired/needed by many before they even think about adopting the new Windows 10 Edge browser. According to my sources, extensions are still a Redstone 1 (not a Redstone 2/Spring 2017) feature of Windows 10.
As seen on Microsoft's Edge Extensions Preview page, the first three supported Edge extensions that testers will get to preview are Microsoft Translator, Reddit Enhancement Suite and Mouse Gestures.
The Translator extension description says it will "translate foreign language pages for 50+ languages." The Reddit one is a "suite of modules" for enhancing Reddit, and the Mouse Gestures extension will "allow customers to perform basic browsing tasks by right-clicking and then gesturing with the mouse."
The link to the extensions page describes how testers will be able to add extensions in preview builds of Edge. That page says testers should download an extension; select run from the download notification; select More (...) and then Extensions; and then select Load Extension, choose the extension folder and select "Select folder."
The ultimate goal for Microsoft is to release Edge extensions through the unified Windows 10 Store, as the preview page indicates.
Microsoft's extensions placeholder page says: "These extensions have been validated by our team and are expected to work with the preview build XXX. We'll be adding more extensions as we build out our extension platform with your help."