FreeCorrector by BenjiBurn
Free, open-source spelling and grammar checker for English and French. Underlines your mistakes in every text field and fixes them in one click. 100% local: your writing never leaves your computer.
Available on Firefox for Android™Available on Firefox for Android™
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About this extension
FreeCorrector checks your writing wherever you type: emails, social media, forms, chat apps, online documents… Free, with no account, no subscription and no ads.
How it works
• Mistakes are underlined as you type: red for spelling, orange for grammar, blue for typography.
• Click an underlined word to see the recommended fix, with the other suggestions right below.
• A counter at the bottom right of the field shows how many mistakes there are. Click it for the full list.
• The "Correcteur" page (toolbar menu) lets you paste a long text, see every mistake and fix them all in one click.
English and French
The language is detected automatically for each paragraph, so an email mixing both languages is checked in both. English: your/you’re, its/it’s, their/there/they’re, subject-verb agreement, tenses, “should of”, typos and more. French: agreement, conjugation, homophones, past participles, subjunctive, accents, capitals and punctuation.
Your writing stays yours
Everything is checked inside your browser. FreeCorrector sends nothing over the Internet, collects no data and even works offline. The browser itself blocks any network connection from the extension.
Also
• Personal dictionary.
• Turn it off on the sites you choose.
• Picky mode for fine typography.
• Also works in rich-text editors (webmail, social networks, online tools).
• Undo with Ctrl+Z after a fix.
Open source
FreeCorrector is free software (GPL v3). It builds on two open-source engines, Harper for English and Grammalecte for French, and adds its own rules and context-aware ranking of suggestions. Source code: https://github.com/BenjiBurn/FreeCorrector
Note: the extension’s interface is in French for now; an English version is coming.
Made by BenjiBurn.
How it works
• Mistakes are underlined as you type: red for spelling, orange for grammar, blue for typography.
• Click an underlined word to see the recommended fix, with the other suggestions right below.
• A counter at the bottom right of the field shows how many mistakes there are. Click it for the full list.
• The "Correcteur" page (toolbar menu) lets you paste a long text, see every mistake and fix them all in one click.
English and French
The language is detected automatically for each paragraph, so an email mixing both languages is checked in both. English: your/you’re, its/it’s, their/there/they’re, subject-verb agreement, tenses, “should of”, typos and more. French: agreement, conjugation, homophones, past participles, subjunctive, accents, capitals and punctuation.
Your writing stays yours
Everything is checked inside your browser. FreeCorrector sends nothing over the Internet, collects no data and even works offline. The browser itself blocks any network connection from the extension.
Also
• Personal dictionary.
• Turn it off on the sites you choose.
• Picky mode for fine typography.
• Also works in rich-text editors (webmail, social networks, online tools).
• Undo with Ctrl+Z after a fix.
Open source
FreeCorrector is free software (GPL v3). It builds on two open-source engines, Harper for English and Grammalecte for French, and adds its own rules and context-aware ranking of suggestions. Source code: https://github.com/BenjiBurn/FreeCorrector
Note: the extension’s interface is in French for now; an English version is coming.
Made by BenjiBurn.
Rated 4 by 3 reviewers
Permissions and data
Required permissions:
- Access your data for all websites
Data collection:
- The developer says this extension doesn't require data collection.
More information
- Add-on Links
- Version
- 1.2.6
- Size
- 10.52 MB
- Last updated
- 4 hours ago (Oct 21, 2026)
- Related Categories
- Version History
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The developer of this extension asks that you help support its continued development by making a small contribution.