Grammarly AI detector
Vendor Grammarly Official site grammarly.com/ai-detector How this card is sourced
Updated · AI Detector Index editors
Grammarly's AI Detector checks text for output from ChatGPT, GPT-6, Gemini, Claude and Microsoft Copilot, with a free check that needs no sign-up, according to the product page read on 8 November 2026 (grammarly.com). Grammarly is a text-only detector sold inside a writing suite, and the card is the one in this batch with the fewest ranking fields: no study record, no numeric false positive rate, no monthly free allowance and no language count. How this card is sourced explains the rules; the full detector index holds the other twenty-one cards.
What Grammarly detects
| Field | Value | Source |
|---|---|---|
| Content types detected | Text | grammarly.com/ai-detector |
| Generators covered | ChatGPT, GPT-6, Gemini, Claude, Microsoft Copilot, Grammarly, other tools | grammarly.com/ai-detector |
| Free tier | Free AI Detector, no sign-up needed; allowance per period not published. On the plans page the Detect AI generated text row is unchecked for Free and checked for Plus and Pro. | grammarly.com/plans |
| Integrations | Browser extension (Chrome, Safari, Firefox, Edge), Grammarly for MS Office, Grammarly for Google Docs, Desktop (Windows, Mac), Mobile (iPhone, iPad, Android) | grammarly.com/ai-detector |
| Ownership | Superhuman Platform (footer: 2026 (c) Superhuman Platform; Company menu lists Superhuman and GPTZero) | grammarly.com/ai-detector |
Grammarly covers one modality, text. The product page names ChatGPT, GPT-6, Gemini, Claude, Microsoft Copilot, Grammarly's own generative features and other tools as the generators covered (grammarly.com/ai-detector, read 8 November 2026).
On edited AI text, Grammarly says: "Lightly edited AI-generated text may evade detection." The same page describes Grammarly Authorship, which "automatically categorizes your text based on where it came from (AI, an online database, typed by you, etc.)". Source: grammarly.com/ai-detector, read 8 November 2026. Authorship is a provenance record kept while writing, a different mechanism from the detector's statistical score.
Grammarly's footer reads "2026 (c) Superhuman Platform", and the Company menu lists Superhuman and GPTZero (grammarly.com/ai-detector, read 8 November 2026). The GPTZero card covers the detector that announced plans to join the same group on June 23, 2026. Integrations are a browser extension for Chrome, Safari, Firefox and Edge, Grammarly for MS Office, Grammarly for Google Docs, desktop apps for Windows and Mac, and mobile apps for iPhone, iPad and Android (grammarly.com/ai-detector, read 8 November 2026).
Limits and plans
| Plan | Price | Limits | Checked on |
|---|---|---|---|
| Pro (annual) | $12 USD / member / month, billed annually | Everything in Free, rewrite full sentences, adjust your writing tone, stay on-brand, generate text with 2,000 AI prompts; access to the AI Detector agent. | |
| Pro (monthly) | $30 when billed monthly | Same as Pro (annual). | |
| Enterprise | Contact sales; available through Superhuman Go. |
Grammarly offers the AI Detector free with no sign-up. On the plans page the "Detect AI generated text" row is unchecked for Free and checked for Plus and Pro (Grammarly plans page, read 8 November 2026). The free check therefore runs on the public detector page, while the detector inside the paid product is a Plus and Pro feature.
Prices below come from the Grammarly Pro page, read 8 November 2026, in USD.
Grammarly says of its model: "Our detection model was trained on tens of thousands of texts, including both human-written and AI-generated text created before 2021" (grammarly.com/ai-detector, read 8 November 2026).
What the vendor claims
Achieves 99% detection accuracy and ranks #1 on RAID's independent benchmark, outperforming other leading AI detectors.
Grammarly says: "Achieves 99% detection accuracy and ranks #1 on RAID's independent benchmark, outperforming other leading AI detectors." The sentence is from the Grammarly AI Detector page, read 8 November 2026. The FAQ on the same page says: "No AI detector is 100% accurate"; this card carries the 99% sentence as the claim and the FAQ sentence as the caveat, since the two are not a numeric conflict.
On false positives, Grammarly says: "Reduced false positives: Designed to avoid wrongly flagging human-written text." (grammarly.com/ai-detector, read 8 November 2026). Grammarly gives no numeric false positive rate, which keeps the card out of the false positive rate ranking.
Grammarly also says: "AI detection should never be used as a standalone verification method" (grammarly.com/ai-detector, read 8 November 2026). A 99% headline from a vendor that trained on text created before 2021 describes a benchmark result, and a reader has no way to check from the page which RAID split or threshold produced the figure.
What independent studies found
No study in the index has tested Grammarly's detector; the detectors with a study record are listed in the independently tested ranking, and the RAID record in this index covers GPTZero, Originality.ai, Winston AI and ZeroGPT.
Where Grammarly appears in the index
Rankings
Fits these use cases, questions and comparisons
- AIDI-U-13AI detectors for government and public sector buyers
- AIDI-Q-01Is there a 100% accurate AI detector? What published tests show
- AIDI-Q-11Is an AI detector itself an AI? The four detection methods behind the cards, each sourced
- AIDI-C-06GPTZero vs Grammarly's AI Detector: the 14 fields and the evidence side by side
Grammarly qualifies for none of the four rankings on the fields read 8 November 2026 (detectors.json): the study count is 0, no numeric false positive rate is on the vendor pages, the free allowance has no stated period, and no language list or count is published on the product page. The card appears in the full table on the home page and in the detector hub with the same 14 fields as every other card.
Grammarly fits business through per-member Pro pricing and the Enterprise tier through Superhuman Go, and recruiters through the free no-sign-up check on plain text (grammarly.com/pro, read 8 November 2026). The nearest cards are QuillBot, another writing-suite detector with a bundled plan, and GPTZero, the sister product under Superhuman.
GPTZero vs Grammarly, added 9 November 2026, sets this card beside the index's most-tested detector, which shares its platform owner: twelve study records against none.
Questions about Grammarly AI detector
Is Grammarly's AI detector free?
Yes on the public page. The product page read 8 November 2026 offers the AI Detector free with no sign-up. Inside the product, the plans page shows "Detect AI generated text" unchecked for Free and checked for Plus and Pro, with Pro at $12 USD per member per month billed annually.
How accurate does Grammarly say its detector is?
99%, and ranked #1 on RAID, per the product page read 8 November 2026. The same page's FAQ says no AI detector is 100% accurate and that lightly edited AI text may evade detection. No study in the index has measured Grammarly's detector.
Does Grammarly publish a false positive rate?
No numeric rate. The product page read 8 November 2026 says the detector is "Designed to avoid wrongly flagging human-written text" and gives no percentage, so the card does not appear in the false positive rate ranking, where every row needs a number.
What is the difference between Grammarly's detector and Authorship?
The detector scores pasted text statistically; Authorship records where text came from as you write, as AI, an online database or typed by you, per the product page read 8 November 2026. Authorship is a provenance log, so a writer can show their process rather than argue with a score.
Sources and revisions
Sources
- grammarly.com/ai-detectorRead 8 November 2026
- grammarly.com/plansRead 8 November 2026
- grammarly.com/proRead 8 November 2026
Revision log
- Card created2026-11-09: gptzero vs grammarly comparison linked (fifth wave)
