Grammarly

Cross-app AI writing assistant that catches errors, rewrites paragraphs, and adjusts tone in the tools you already use.

Freemium· Free; Pro $12/mo annual or $30/mo; Enterprise customWritingProprietary + multi-model

Best for

Pick Grammarly if you want a writing coach embedded in every app you already use and don't want to run your own LLM workflow.

Skip if

Skip it if you need programmatic writing APIs, want full control of the model, or already pay for ChatGPT/Claude and prefer prompting directly.

Grammarly is the incumbent AI writing assistant, running as a browser extension, desktop overlay, and mobile keyboard that inserts itself into Gmail, Docs, Word, Slack, LinkedIn, and just about any text field on the web. The core value is real-time grammar, clarity, and tone feedback plus one-click paragraph rewrites, with a growing shelf of purpose-built AI agents for resume drafting, citation finding, AI detection, humanizing, and reader-reaction analysis.

Where it differentiates from raw ChatGPT usage is surface area and workflow: instead of copy-pasting into a chat window, Grammarly rides along inside whatever app you're already writing in and respects your existing sentence. The Free tier covers basic corrections and 100 generative prompts; Pro (marketed as Plus) runs $12/month billed annually or $30/month monthly with 2,000+ prompts, style guides, and full rewrites; Enterprise adds SSO, confidential mode, and unlimited seats for the 50,000+ organizations already on it.

There is no public generative API for developers; Grammarly is a consumer/enterprise SaaS, not a model provider. It's closed-source, and the underlying models are a proprietary blend layered over unnamed third-party LLMs. For teams that want writing consistency without training everyone to prompt an LLM, it's still the safest default.

Editor's take

Still the default answer for 'AI writing assistant' for a reason: the distribution across every text field on your machine is unmatched. The Free tier is enough for most people; Pro only earns its price if you write for a living or need the style-guide enforcement. Power users on a Claude or GPT subscription can probably skip it.

— The AI Tool Bible editorial team