It's nice that iOS 15 added WebExtensions support to Safari. It's not so nice that the feature only works with Safari, and that other browsers like Firefox are excluded even though Apple mandates that they use Safari's browser engine and does not allow them to "download, install, or execute code which introduces or changes features or functionality of the app".* It's also not so nice that a developer must pay Apple's $99/year developer fee to keep a browser extension for Safari in the App Store, the only way to publish browser extensions on iOS.

* https://developer.apple.com/app-store/review/guidelines/

I'm not sure if it's a policy issue here, there's an existing browser[0] that seems to support them.

Subscribe here for updates: https://github.com/mozilla-mobile/firefox-ios/issues/9155

[0]: https://apps.apple.com/jm/app/kagi/id1484498200

Kagi was last updated in September 2020. If it manages to get an update approved by Apple and set a precedent in the App Store, I'll be glad to see it.