Loom <a href="https://www.loom.com/" rel="nofollow">https://www.loom.com/</a> started as a chrome extension.<p>Grammarly has done really well <a href="https://www.grammarly.com/" rel="nofollow">https://www.grammarly.com/</a>
Streak CRM (YC S11) [<a href="https://www.streak.com/" rel="nofollow">https://www.streak.com/</a>]<p>I think Hunter (<a href="https://hunter.io" rel="nofollow">https://hunter.io</a>) started as a chrome extension<p>Password managers like LastPass (<a href="https://www.lastpass.com/" rel="nofollow">https://www.lastpass.com/</a>) rely on their browser extensions for convenience and usability
I think that Rapportive started as a Chrome extension. I don't know much about the business but I believe the founder went on to start Superhuman.