Grammarly

Grammarly is the world's most widely used AI writing assistant, installed by over 50 million people as a browser extension, desktop app, and integration for Microsoft Word, Google Docs, Slack, and dozens of other platforms. It analyzes your writing in real time as you type, flagging grammar errors, spelling mistakes, unclear phrasing, and tone inconsistencies — across every surface where you write.

The free tier catches most grammar and spelling errors, which is genuinely useful for everyday writing. Grammarly Premium ($12/month) unlocks the more powerful features: clarity rewrites that simplify complex sentences, vocabulary suggestions, plagiarism detection, and the tone detector that tells you how your writing sounds — formal, casual, confident, or aggressive — so you can adjust before hitting send.

Grammarly's business and team plans add a shared style guide, brand tone consistency checking across team members, and analytics on writing quality. The biggest limitation is creative writing: Grammarly's suggestions are tuned for clear, standard English and will often flag intentional stylistic choices — fragmented sentences, unconventional punctuation, or dialect — as errors. It is most valuable for professional communications, academic writing, and anyone writing in English as a second language.