QuillBot

QuillBot began as a paraphrasing tool and is now an all-round AI writing assistant, with a paraphraser, grammar checker, AI detector and humaniser. It is made by QuillBot, a Learneo business, and Learneo also owns Course Hero and LanguageTool. With about 6 million Chrome users and a 4.7 rating, it is far larger than most picks here.

In a browser it works inside text fields on most sites, with grammar suggestions, paraphrasing and chat, and it asks for access to all sites. The free plan gives two paraphrase modes and Premium adds more. It is listed on Chrome and Edge, while Mozilla shows its Firefox listing as disabled by the developer.

Read the data terms before installing. QuillBot's help centre says that since a privacy policy update on 8 November 2025 it stores text inputs from browser extension users by default, with an opt-out. A separate opt-out for AI training exists, but only for account holders, and Team Plan inputs are excluded from training by default. The default for the training control is not clear from the page we read, so check the Data and Privacy menu in the extension settings. Use it if paraphrasing is the job, but not for sensitive text.