Grammarly AI Detector: Check Your Text Free
Paste your text below for an instant AI check — then see exactly how Grammarly's own AI detector performed in our hands-on 2026 accuracy test.
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Independent tool — not affiliated with Grammarly. Results are estimates, not proof of authorship.
Our 2026 hands-on test
How accurate is Grammarly's AI detector?
We tested Grammarly's AI detection on 12 passages of 450–700 words across three content types in March 2026. The short answer: strong on raw AI text, trustworthy on human writing, weak on edited AI.
| Content type tested | Result | What it means |
|---|---|---|
| Raw, unedited AI text (GPT-4) | 94% detected | Reliable first check for copy-pasted chatbot text. |
| Authentic human writing | 6% false positives | Low risk of your own writing being wrongly flagged. |
| AI text edited or humanized | 22% detected | Misses most refined AI text — do not rely on it alone for high-stakes checks. |
Grammarly itself describes the score as an estimate, not proof of authorship — the right way to read any AI detector result.
Method: 4 raw AI passages, 4 human passages, 4 edited-AI passages; neutral nonfiction topics; each 450–700 words.
What is Grammarly's AI detector?
Grammarly added a free AI detector to its writing suite: paste text and it returns a percentage estimating how much reads as AI-generated. It's fast, free, and built into a tool millions already use — which makes it many people's first stop for an AI check.
The trade-off is depth. Grammarly gives you a single overall percentage without sentence-level highlighting, and — as our test shows — its accuracy drops sharply once AI text has been edited. For anything that matters, verify with a second detector and keep your drafting history.
How to check your text
Paste your text
Drop your draft into the checker above — essays, articles, emails, any prose.
Get an instant verdict
Our detector analyzes the text against the patterns of ChatGPT, GPT-4, Claude, Gemini, and other models — with sentence-level detail, not just one number.
Cross-check what matters
For high-stakes text, compare results across detectors (Grammarly, GPTZero, ours) — agreement across tools is far more meaningful than any single score.
Grammarly's detector vs. this one
Both are free. Here is the honest difference, based on our own testing:
| Feature | Grammarly | humantext.pro |
|---|---|---|
| Raw AI text detection | 94% (our test) | Multi-model check tuned for current generators |
| Edited / refined AI text | 22% (our test) | Trained specifically on edited and paraphrased AI text |
| Result detail | One overall percentage | Score with sentence-level breakdown |
| Sign-up required | Grammarly account | None for the free check |
Frequently Asked Questions
It depends on the content. In our March 2026 test it caught 94% of raw, unedited AI text and wrongly flagged only 6% of human writing — but it identified just 22% of AI text that had been edited or humanized. Treat it as a solid first-pass check, not a final verdict.
Yes. Grammarly's AI detection is available for free with a Grammarly account. The checker on this page is also free and requires no sign-up.
All AI detectors produce some false positives — Grammarly's rate was about 6% in our test, which is low but not zero. Very polished, formulaic, or heavily templated writing is flagged most often. If it happens, keep your drafting history as evidence and cross-check with a second detector.
Mostly no. This was its biggest weakness in our test: once AI text had been revised for tone and sentence variety, Grammarly caught only 22% of it. Detectors trained specifically on edited AI text perform better on this category.
No — Grammarly returns a single overall percentage. If you need to know which parts of a document read as AI-generated, use a detector with sentence-level highlighting, like the one on this page.
Use at least two independent detectors and compare. The free checker above gives a sentence-level breakdown, and our Grammarly alternatives page compares the main options for grammar checking and AI detection side by side.
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