Coda One is a small set of AI writing tools built around one loop: check a draft, then fix what the check finds. The AI Detector is free with no daily limit and no signup, and it marks the specific sentences that read as machine-written instead of just giving a score.

Alongside the detector are an AI Humanizer with 5 free writing modes (Standard, Academic, Blog, Formal, Simple), an AI Rewriter with 5 free tones (Standard, Fluency, Formal, Casual, Concise), and a Grammar Checker. All four are available in the browser and in a Chrome extension. The writing tools are free for 3 runs a day without an account, or 5 with a free account. Built by a small independent team in London.