Wordtune is an AI-powered writing assistant developed by AI21 Labs that helps users rewrite, refine, and polish their writing across the web. Unlike traditional grammar checkers, Wordtune focuses on rephrasing and rewording — letting writers highlight any sentence and instantly see multiple AI-generated variations in different tones (casual, formal) and lengths (shorten, expand). Beyond rewriting, the platform offers Smart Suggestions that help develop ideas with structured tools like Explain, Emphasize, Give an Example, Counterargument, Define, Analogy, and Add a Conclusion. Wordtune also includes AI summarization capable of ingesting long documents and PDFs (up to 500 pages) and producing executive summaries with hyperlinked citations back to source text. The product works as a browser extension across Google Docs, Gmail, Outlook, LinkedIn, Notion, and most web text fields, plus a dedicated Microsoft Word add-in and a standalone editor at wordtune.com. Wordtune is especially popular with non-native English writers, students, marketers, customer support teams, and professionals who want to sound more natural and confident without sacrificing their own voice. Powered by AI21's proprietary large language models, Wordtune emphasizes meaning preservation — rephrasing sentences without changing the original intent — and is trusted by millions of users worldwide as a faster, more nuanced alternative to generic grammar correction.