Grammarly fixes writing where you already write it. ChatGPT fixes writing you paste into a chat box. That gap matters more than quality, because pasting is the step you quietly stop doing.
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Pick Grammarly if you write all day inside other people's software, email, Slack, docs, a ticket queue, and you want the correction to show up there instead of in a second window.
Pick ChatGPT if your problem is the draft and not the comma, and you want something that argues with the structure rather than tidying the sentences you already committed to.
Pick neither if your writing is already fine and the real problem is that you hit send before rereading, which is a habit, not a subscription.
prices checked 2026-10-13 · by dan scutaru
| Grammarly | ChatGPT | |
|---|---|---|
| price | free tier · from $30/mo | free tier · from $8/mo |
| free tier | Spelling and grammar corrections, tone insights and 100 AI prompts per month. | Unlimited text chats with GPT-6 Luna (subject to abuse guardrails), with limited uploads, image generation, voice, deep research, memory and Codex access. |
| runs on | web, windows, mac, ios, android | web, ios, android, mac, windows |
| Where it corrects you | In the box you are typing in, through the browser extension and desktop app. Grammarly says over 1 million apps and sites | Mainly in ChatGPT's own window: you paste the text in and copy the fix back |
| How a fix arrives | One underline per issue, accepted or dismissed one at a time | A rewritten version. Ask for a list of changes if you want to see what moved |
| Plagiarism and AI-text checks | Both on Pro. A free AI detector on the web | No plagiarism or AI-text checker in its plan features |
| Your text trains the AI by default | Yes on Free and individual Pro. Off on Enterprise, Education and plans bought through Sales | Yes on Free, Go, Plus and Pro. Off on Business, Enterprise and Edu |
| Model underneath | Superhuman lists OpenAI, Azure, Anthropic and Baseten as generative AI providers | OpenAI's own GPT models |
It works, and on the free plan it costs nothing: paste the text, ask for corrections, get a clean version back. Everyday text chats on ChatGPT Free are unlimited, so there is no counter like Grammarly's 100 AI prompts a month.
What you lose is the choice per error. Grammarly underlines each problem and you accept or dismiss it. ChatGPT hands back a new paragraph, and it tends to fix things that were not broken. An early-2023 study that put the ChatGPT of the time against Grammarly on a standard error-correction test found it made more over-corrections, rewriting phrasing and sentence structure instead of only the error. Read the result against your original before you send it.
Yes, and not only the chat part. Grammarly's help center says the AI behind its ordinary suggestions is integral to the product and cannot be turned off. What you can switch off is the generative layer, the prompts and rewrites, under Feature customization in your account settings. On team and school plans an admin can switch it off for everyone.
So the real difference from ChatGPT is not AI against no AI. It is how much of your text the AI is allowed to write. If your course rules ban AI tools with no exceptions, read them before assuming Grammarly is fine. Whether its edits get flagged by a detector is a separate question, with its own page on Grammarly's AI detector.
The company behind Grammarly renamed itself Superhuman in late 2025, and the product kept its name. The suite now puts Grammarly next to Docs, Superhuman Mail and an agent product called Go. Go was free for everyone through 1 February 2026, and the free plan now gets limited chat access to it.
The odd part is the price. grammarly.com sells Pro at $30 billed monthly or $144 a year. superhuman.com lists its own Pro, which includes Grammarly, Docs and Go, at $15 billed monthly or $12 a month billed annually. We have not bought both, so we cannot tell you the Grammarly inside them is identical. Open both pages before you pay for either.
Tell it what not to touch. Something like: "Proofread this. Fix only spelling, grammar and punctuation. Do not change word choice or sentence order. After the corrected text, list every change you made." That keeps your voice and gives you the change list Grammarly shows by default.
Two more habits. Paste long documents in parts, because the free plan's context window is about 12 pages of text. And if the text is not yours to share, turn off Improve the model for everyone under Settings > Data controls first, because training is on by default on Free, Go, Plus and Pro. Grammarly trains on Free and individual Pro text by default too, with its own switch.
For catching errors in text you already wrote, yes: it flags each one where you type and leaves the rest of the sentence alone. For drafting, restructuring or asking whether an argument holds up, no. Both have free plans, so you do not have to choose to cover both jobs.
Not the ChatGPT app, but it does use OpenAI. Superhuman, Grammarly's parent, lists OpenAI, Azure, Anthropic and Baseten as generative AI providers, and Grammarly says those providers may not train on your text. We found no page saying which model handles which feature.
Yes. Grammarly's free AI detector on the web scores pasted text with no sign-up, and Pro adds a detector agent. In small independent tests it cleared human writing but missed most text from current chatbots, and Grammarly's own help center says no detector can conclusively tell whether AI was used.
Yes. The free plan runs GPT-6 Luna with unlimited everyday text chats, which is all a grammar check needs, while files, images and voice are limited and ads may appear. The full answer →
Yes, for spelling, grammar and tone, with no card. The AI part is 100 prompts a month, and one-click buttons like Improve it count as prompts. The full answer →