On iPhone and iPad, browser extensions only come from the App Store, and Web Highlights is not there yet. So Safari, Chrome and Edge on iOS cannot run it. What does work: paste a link into the Web Highlights reader and highlight the article right there.
Safari on iPhone and iPad only runs extensions that are installed as apps from the App Store. Chrome, Edge and Firefox for iOS do not support extensions at all. Web Highlights has no iOS app yet, so there is nothing to install. This is also true on iPad, even though iPad Safari shows the desktop version of websites.
Tip: create a free account to keep your highlights in your library.

Note: on iPhone, web apps cannot appear in the Share menu of other apps. To save a page from another app, copy its link and paste it into Web Highlights.
Orion, a browser by Kagi, can load some Chrome and Firefox extensions on iPhone and iPad. That support is in beta and covers fewer features than on a computer. We have not tested Web Highlights in Orion, so we cannot promise it works. The reader above is the way we support.
More on extensions on iPhone: Can you use browser extensions on an iPhone?
Not yet. Use the web app at app.web-highlights.com and add it to your Home Screen, and use the reader to highlight articles.
Yes, when you are signed in with the same account on your iPhone and in the extension on your computer. Sync is free for a 7-day trial, then part of the paid plans.
No, you can start highlighting in the reader right away. To keep your highlights in your library, create a free account.
Paste any article link and highlight it in the reader, right on your iPhone.
Open the Reader Mode toolUsing an Android phone? Read how to use Web Highlights on your Android phone.