Grammarly is the world's most-used AI writing assistant, trusted by over 30 million users to improve writing quality in emails, documents, and websites. It checks grammar, spelling, clarity, tone, and plagiarism in real-time across hundreds of platforms (Gmail, Word, Slack, LinkedIn, Twitter, browsers). Launched in 2009, Grammarly evolved from basic spell-check to a comprehensive AI writing coach using large language models.

In our testing, Grammarly caught errors humans regularly miss and suggested tone adjustments that improved email response rates. For non-native English speakers, it's transformative—explains why a sentence is unclear and suggests improvements. For professionals, it prevents embarrassing mistakes in client communication. For marketers, it optimizes copy for persuasiveness.

What makes Grammarly exceptional in 2026 is its ubiquity. It works everywhere you write (Gmail, Teams, LinkedIn, web browsers). The AI understands context—it knows you're writing a formal email vs. a Slack message and adjusts tone suggestions accordingly. The free tier is genuinely useful, making it easy to try before upgrading.

The main differentiators: Grammarly's coverage (works across 500+ apps and browsers) is unmatched. It's trained on billions of high-quality writing samples, making suggestions feel natural. However, the Premium plan is pricier ($12/month or $119/year) than competitors. Some users find notifications intrusive. For non-English languages, coverage is limited.

Best AI Tools for Resume and cover letter writing in 2026

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