Grammarly AI Checker: Detect AI-Generated Text in Your Writing

Grammarly AI checker is a built-in feature of the Grammarly writing assistant that scans your text for signs of AI-generated content. Unlike standalone AI detectors, Grammarly integrates AI detection directly into its editing interface — meaning you can check grammar, style, plagiarism, and AI authorship in a single workflow. It is primarily aimed at writers, students, and professionals who want to ensure their content reads as authentically human before publishing or submitting.

Grammarly’s AI detection is available on the Premium and Business plans, with limited access on the free tier. It is distinct from Grammarly’s AI writing assistant features — the checker identifies AI-written text, while the writing assistant helps you produce or improve text. Understanding the difference matters, especially if you use Grammarly’s own AI tools and then want to check whether your final draft will be flagged.

How to Use the Grammarly AI Checker

1. Open Grammarly and paste your text. Go to the Grammarly Editor (app.grammarly.com) or open the Grammarly desktop app. Paste the text you want to check into the editor. You can also upload a supported file format (.docx, .txt, .odt).
2. Open the “Plagiarism” or “Authorship” panel. In the right-hand sidebar, navigate to the full report. Depending on your plan, you will see an option to check for AI-generated content under the “Authorship” or writing insights section.
3. Run the AI detection check. Click the check. Grammarly processes the document and returns a result within seconds, flagging passages that show statistical patterns consistent with AI-generated writing.
4. Review highlighted sections. Grammarly highlights specific sentences or paragraphs it classifies as potentially AI-written. Review each flagged section in context — a single flagged sentence does not mean the entire document is AI-generated.
5. Export or revise. If you are editing your own work, use the feedback to revise flagged sections before submission. If you are reviewing someone else’s writing, use the report as supporting context, not a definitive verdict.

What Does Grammarly AI Detection Check For?

Grammarly’s AI detection model works by analyzing statistical patterns in writing that differentiate human-authored text from machine-generated text. The core signals it evaluates include sentence structure uniformity, word choice predictability, and the overall entropy of the text — how varied and “surprising” the writing is at a linguistic level.

Human writing tends to exhibit higher variation in sentence rhythm, occasional informal constructions, and a degree of unpredictability that reflects individual voice. AI-generated text — especially from models like ChatGPT, Claude, and Gemini — tends to be grammatically clean, structurally consistent, and statistically predictable. These properties make it detectable to models trained to recognize the difference.

Grammarly’s detection layer is trained on a large corpus of both human and AI-generated text and is updated as new AI models emerge. However, because Grammarly is primarily a writing tool, its detection model is calibrated toward general professional and academic writing — it performs best in those contexts and may be less reliable on highly technical, creative, or domain-specific content.

One important distinction: Grammarly does not provide a sentence-level heatmap in the same way GPTZero does. It flags passages and provides an overall assessment, but the granularity is lower. If you need detailed sentence-by-sentence breakdown, a dedicated tool like GPTZero may be more informative.

Is Grammarly AI Checker Free?

Grammarly’s AI detection feature is not available on the free plan in full. Access depends on your subscription tier:

Feature	Free	Premium	Business
Grammar and spell check	Yes	Yes	Yes
Style and clarity suggestions	Limited	Yes	Yes
AI-generated text detection	No	Yes	Yes
Plagiarism checker	No	Yes	Yes
Authorship insights	No	Yes	Yes
Team management and reporting	No	No	Yes

If you need a free AI detection tool with no subscription required, GPTZero or our own checker are better starting points. Grammarly’s AI detection is most valuable when you already use Grammarly for editing and want a unified workflow — not as a standalone free detection solution.

How Accurate Is the Grammarly AI Checker?

Grammarly’s AI detection accuracy is considered moderate compared to purpose-built tools like GPTZero or Copyleaks. It performs reasonably well on standard AI-generated essays and professional content but has documented limitations:

• False positives on clean, formal writing. Highly polished academic or business writing can score as AI-generated because it shares surface-level properties — uniform structure, precise vocabulary, minimal colloquialisms — with AI output. This is a known limitation of all statistical detection models, not just Grammarly’s.
• Lower sensitivity on edited AI content. If AI-generated text has been substantially rewritten by a human, Grammarly may not flag it reliably. The same is true for most detection tools.
• Less granular than specialized tools. Grammarly does not provide the same depth of sentence-level analysis as GPTZero. If you are trying to identify exactly which sentences in a document were AI-written, a dedicated checker will give you more actionable data.

For most individual use cases — checking your own work before submission, or doing a quick review of a document — Grammarly’s detection is a useful signal. For institutional or academic integrity decisions, it should be used alongside other tools and human judgment.

Does Grammarly Count as AI Writing?

This is one of the most common questions students ask — and it is a different question from how the AI checker works. If you use Grammarly’s AI writing features (such as “Rewrite with AI” or AI-generated suggestions) to produce or heavily revise your text, that output may be flagged by AI detectors, including GPTZero and Turnitin.

Using Grammarly’s grammar and style checker — which corrects errors and suggests edits without generating new text — does not produce AI-detectable output in the same way. The distinction is between AI-assisted editing (grammar corrections, word suggestions) and AI-generated writing (rewriting paragraphs or generating new content from prompts).

For a full breakdown of this distinction, see our article on does Grammarly count as AI.

Grammarly AI Checker vs GPTZero vs Other Tools

Tool	Best For	Free Tier	Sentence-Level Detail	Accuracy
Grammarly AI Checker	Writers already using Grammarly	No (Premium only)	Moderate	Moderate
GPTZero	Academic essays, educators	Yes (5,000 chars)	High (sentence heatmap)	High
SafeAssign	Blackboard LMS institutions	Via institution only	Low	Moderate
Copyleaks	Multilingual content, publishers	Yes (limited)	High	High
Turnitin	University submissions	No (institutional)	High	High

Grammarly’s main advantage is workflow integration — if you already edit in Grammarly, you do not need to copy your text into a separate tool. Its main disadvantage is that AI detection requires a paid plan and offers less granularity than dedicated tools.

Try an AI Checker Now

Want to check whether your text will be flagged as AI-generated? Use the button below to run a free check — no account required. Get sentence-level results in seconds and see exactly which parts of your document are at risk of being flagged.

Check Your Text for AI →

Frequently Asked Questions