A Grammarly AI detector alternative with a free sentence map
IsThisAiWritten is a free Grammarly AI detector alternative for English text: it shows a sentence map on every check, has no length limit, needs no account and never uploads your writing. Grammarly's free AI detector takes up to 25,000 characters and returns a percentage: how much of your text appears to be AI-generated. Seeing which passages drove that number is part of Grammarly Pro.
Use IsThisAiWritten when you want sentence-level detail without paying, or when the text is long or private enough that you would rather it stayed on your own computer: there is no account, no length limit and no upload. Stay with Grammarly if you already write in it every day or want its Authorship record of how a document was produced.
Grammarly AI detector alternative: the comparison
Grammarly details come from its own pages at the time of writing.
| IsThisAiWritten | Grammarly AI Detector | |
|---|---|---|
| Price for basic use | Free, including the sentence map | Free score. Sentence-level detail needs Grammarly Pro, a paid plan |
| Sign-up required | No | No sign-up step described for the free scan. Pro needs an account |
| Character limit per check | No limit. Minimum 50 words | 25,000 characters in the free text box |
| Daily limit | None | Not stated |
| Where your text is processed | In your browser. Never uploaded | On Grammarly's servers |
| Data stored | Nothing | Parent company's policy says collected content can train its AI models unless you switch that off in account settings |
| Long documents (novels, theses) | One pass, at any length | Anything over 25,000 characters must be split |
| Sentence-level highlighting | Free sentence map, relative within your text | Pro only, through the AI Detector agent |
Why look for an alternative to Grammarly's AI detector?
Grammarly says its detector achieves 99% detection accuracy and ranks first on RAID, an independent benchmark. The free version's limit is what it shows you: a percentage on its own is hard to act on. If Grammarly tells you 40% of your essay appears AI-generated, the useful question is which 40%. Grammarly's FAQ says that the view of exactly which parts may sound AI-generated comes with the AI Detector agent in Pro. The free box also stops at 25,000 characters, which a long report or a dissertation chapter will pass.
Privacy is the second reason. Grammarly now operates under Superhuman, and Superhuman's privacy policy says it uses the information it collects to train its AI models. You can turn that off with a training control in your account settings. It is a reasonable arrangement, as long as you know to change the setting.
A third point is less obvious. In June 2026, Superhuman also announced it was acquiring GPTZero, and Grammarly's site now lists both under its company links. If you were planning to move from Grammarly's detector to GPTZero for an independent second opinion, they now share a parent.
Editing with Grammarly can trip AI detectors
This is worth knowing before you run any check. Originality.ai's FAQ says tools that use AI to rewrite or edit copy, naming some Grammarly features, can cause false positives. Copyleaks' detector page makes a similar warning about Grammarly. Neither means you did anything wrong, but it does mean a high score on a heavily edited draft is hard to interpret.
Like any detector, ours can be wrong in both directions, so treat a result as a reason to look closer, not as proof. Our methodology page explains how it is tested. Whatever tool you use, keep your drafts and version history. Our guide on being wrongly flagged goes through what helps.
What IsThisAiWritten gives you for free
A sentence map without Pro
Every check includes a sentence map that ranks the sentences in your text by how AI-like they look relative to the rest. It won't label each line as human or AI, but it shows where to look first, which is usually what you need when revising.
No size limit
Paste a whole report, thesis or book. There is no character cap and no daily allowance, so a dissertation chapter that overflows Grammarly's 25,000-character box goes in whole. See AI detection for long documents.
No training control to remember
With Grammarly, keeping your writing out of AI training means finding the right switch in your account settings. Here there is no account and no switch, because the check runs inside your browser and your text is never sent to us. The private AI detector page explains how to confirm that.
A verdict that can say "Inconclusive"
Instead of a bare percentage, the report gives one of four outcomes (Human, Mixed, AI or Inconclusive) with a confidence word. When the text is too short or the evidence points both ways, it says so rather than guessing, which is more useful than a middling score when you are deciding what to revise.
Grammarly records how a document was written. Its Authorship feature sorts the text in a document by where it came from (typed by you, generated by AI, taken from an online source and so on) so you can show your work. For a student worried about a false accusation, that kind of record is worth more than any detector score.
Pro adds plagiarism checks. Grammarly also offers citation tools and an AI Rewriter, and it all runs in apps and extensions for Chrome, Safari, Firefox, Edge, Office and Google Docs that many people already have open.
Keep using Grammarly if you draft in it daily or need a record of how a document was written.
Other Grammarly AI detector alternatives
GPTZero gives sentence-by-sentence highlights and checks up to 10,000 characters without an account, though it now shares a parent company with Grammarly (GPTZero alternatives). QuillBot separates AI-written text from AI-refined text and allows 1,200 words per free scan (QuillBot alternative). Scribbr offers unlimited free checks of up to 1,200 words and says it does not store submissions (Scribbr alternative).
Sources
- Grammarly AI Detector and FAQ (character limit, accuracy claim, Pro features, company links), checked October 2026
- Grammarly plans, checked October 2026
- Superhuman privacy policy (Grammarly), checked October 2026
- Engadget: Superhuman has acquired GPTZero, checked October 2026
- Originality.ai FAQ (false positives from AI editing tools), checked October 2026
- Copyleaks AI Detector (note on Grammarly), checked October 2026
- GPTZero, checked October 2026
- QuillBot AI Detector, checked October 2026
- Scribbr AI Detector, checked October 2026
Is this AI written? Check it now.
Free, no sign-up, no word limit. The check runs in your browser, so your text never leaves your device.
Check text freeIsThisAiWritten is not affiliated with, endorsed by or sponsored by any company named on this page. Product names belong to their owners. Facts about other products come from their public pages on the date shown and may have changed since.