One that comes to mind is the Rakuten add-on (formerly Ebates) - Rakuten is definitely not a stand-alone Chrome extension but the service it provides through the Ebates extension is tied specifically to browsers.
GRAMMARLY - I've heard from people close to the team that annual revenue is $150mm+ and they're extremely profitable (at least profitable enough to be one of the few, if not the only, Chrome extension to buy outdoor ads).
not sure but mixmax.com is one strong chrome extensions software. It does has gmail as well as standalone web app.
Definitely not $100 million, but Rapportive—an add-on for Gmail (via Chrome or Firefox) that added contact info and more to your emails—was acquired by LinkedIn for $15 million. It also had an Outlook add-on, so wasn't solely a browser add-on, but close. That team then went on to build Superhuman more recently.
I believe Loom.com is mostly used via the Chrome extension. It does have a standalone web-app and recently native apps, but their primary user interface was browser extensions.
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