The Harper Firefox Extension

Harper is available for the millions who rely on Firefox for fast, private, and independent browsing. Unlike most grammar tools, Harper's Firefox extension performs all analysis locally—never sending your text to the cloud. Emails, chat messages, blog posts, and comments benefit from real-time grammar improvements, with your privacy intact.

A screenshot of the Firefox extension in use.

To install, head to the Firefox Add-ons site and select 'Add to Firefox'.

Curious how it works? The Firefox extension runs entirely on harper.js , our open-source JavaScript library.

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