Browser security will limit some features compared to the regular application, but all three extensions will read most ZIM files without problem.
These extensions do not have a built-in library. You will need to get your zim files directly from the online library.
Installable Progressive Web App (PWA)
Just visit https://pwa.kiwix.org/ in Chrome, Edge or Firefox for our PWA version. In Chrome and Edge, you can install it directly from within the app, and in Firefox, you can bookmark it. It caches its own code, so it can run offline.
All source code available on Github.