Grammarly

Grammarly is the ubiquitous AI-powered writing assistant focused on correctness, clarity, and tone. It goes beyond basic spelling to offer advanced grammar, punctuation, and style suggestions across emails, documents, and social media via its browser extension and desktop apps. Its premium tier includes a plagiarism checker and full-sentence rewrites. With a free core version and paid subscriptions, it targets students, professionals, and anyone who writes regularly.

It ranks highly due to its unparalleled market penetration, reliable core editing features, and seamless integration into daily workflows, though it's less focused on long-form generation.