Grammarly AI Checker Review | Features, Pricing, and accuracy

Grammarly is one of the most trusted writing tools in the world. So when it added an AI checker feature in August 2024, millions of users naturally wondered: is it any good?

We tested Grammarly's AI checker extensively comparing it against AI Checker, Copyleaks, and GPTZero across multiple content types. We checked blog posts, academic papers, marketing emails, and humanized AI content. Here is everything you need to know before deciding whether Grammarly's AI checker is right for you.

What is Grammarly?

Grammarly is a cloud-based writing assistant launched in 2009. It started as a grammar checker and evolved into a full writing suite covering grammar, spelling, punctuation, style, tone, clarity, and plagiarism detection.

Today, it is used by over 30 million people daily, including students, professionals, marketers, and content writers. Its browser extension works across Gmail, Google Docs, LinkedIn, and 500,000+ other platforms.

In August 2024, Grammarly added an AI-generated text detector to its suite designed to identify whether content was written by a human or an AI tool like ChatGPT.

Who Needs Grammarly's AI Checker?

Several types of users have a genuine interest in AI detection:

Teachers and Educators want to know whether student essays were written by a human or generated by AI. Academic integrity is increasingly at risk as AI writing tools become more accessible.

Recruiters and HR Teams screening writing samples from job applicants want to verify whether the applicant actually wrote the content themselves.

Bloggers and Content Managers want to verify that their writers are producing original human content rather than submitting AI-generated drafts.

Writers Using AI as a Tool sometimes want to check whether their AI-assisted content reads too robotically before publishing and use detection as a self-editing step.

Students want to self-check before submission to make sure their genuine work does not get incorrectly flagged by their institution's detection systems.

Main Features of Grammarly

1. Grammar and Spell Check

Grammarly's core feature. It flags errors in real time, catches contextual spelling mistakes, and fixes subject-verb agreement issues that basic spell checkers miss. This remains the strongest part of the Grammarly product.

2. Style and Clarity Suggestions

Beyond correcting errors, Grammarly identifies passive voice overuse, wordiness, repetitive phrasing, and unclear sentence structure. These suggestions genuinely improve writing quality.

3. Plagiarism Detection

Available in Premium, this feature compares your text against web content and academic databases. It is useful for everyday needs but less comprehensive than dedicated academic tools like Turnitin.

4. Tone Detector

Grammarly analyzes whether your writing sounds formal, casual, confident, or aggressive and suggests adjustments. Useful for professional emails and client-facing content.

5. AI-generated Text Detector

The newest addition. Paste any text and Grammarly returns a percentage score indicating how much of it appears to be AI-generated. Simple to use, but as our testing revealed, the accuracy has significant limitations.

6. Browser Extensions and App Integrations

Grammarly works inside Gmail, Google Docs, Microsoft Word, LinkedIn, and most text fields across the web making it one of the most convenient writing tools available.

Grammarly AI Checker Pricing

Plan	Price	What You Get
Free	$0/month	Basic grammar check, limited AI detection (10,000 characters)
Pro	$12–$30/month	Full AI detection, plagiarism check, style suggestions, 2,000 AI prompts
Enterprise	Contact sales	Everything in Pro + dedicated support, unlimited AI prompts, team management

Important note: The AI detection feature in the free plan is limited to 10,000 characters per scan roughly 1,500 to 2,000 words. Longer documents must be split into chunks. Full, unrestricted AI detection requires a Pro subscription. For comparison, AI Checker offers a free tier with no account required, and no character-per-scan restrictions on standard checks.

Read More - Surfer SEO Review - Is It a Good AI Content Detector?

Testing the Accuracy Grammarly's AI Checker

We ran three tests using the same content across Grammarly, AI Checker, and Copyleaks.

Step 1- Generate ChatGPT Paragraph

We started by having ChatGPT produce a short paragraph. The content was a straightforward piece about the benefits of mindful meditation. Nothing too fancy, but definitely AI-generated. You can see a snippet in this screenshot-

Step 2- This ChatGPT Paragraph check in AI checker

Next, we pasted the same text into AI checker. The interface was simple, and it spat out a verdict quickly. The result? It flagged the paragraph as AI-generated with a high confidence score. That means AIchecker was pretty sure it was machine-written.

Step 3- This ChatGPT Paragraph check in copyleaks AI detector

We also tested the Copyleaks AI detector. This tool has gained attention for its detailed breakdown of how “human” vs. “AI” your text appears. Copyleaks also identified the snippet as heavily AI-influenced. The interface was a bit more technical than AIchecker, but it provided deeper insights into the probability scores.

Step 4- Also this ChatGPT paragraph check in Grammarly's AI Detectors

Finally, we went to Grammarly’s AI Checker. We pasted the same paragraph into Grammarly’s text editor. After a moment, it offered a brief statement claiming it was “likely AI-generated.” However, the confidence didn’t seem as robust as AIchecker or Copyleaks’. Grammarly’s interface is minimal, which can be good for quick reads, but it doesn’t give a deep percentage breakdown or any advanced metrics.

Grammarly AI Checker vs AI Checker vs Copyleaks

Feature	Grammarly	AI Checker	Copyleaks
Detection Accuracy	Low–Medium	99%+	~75–95%
Sentence-Level Highlighting	❌ No	✅ Yes	✅ Yes
Consistent Results	❌ No	✅ Yes	✅ Yes
False Positive Rate	High	Very Low	Low
Humanized AI Detection	❌ Weak	✅ Strong	✅ Good
Free Tier	Limited	✅ No signup needed	Trial only
Plagiarism Check	Premium only	✅ Included	✅ Yes
Price	$12–$30/mo	Affordable tiers	$10.99/mo
SEO Content Checking	❌ No	✅ Yes	❌ No
Best For	Writing assistance	AI detection + SEO	Enterprise use

The Verdict

AI Checker gave the clearest, most actionable results across every test. It correctly identified pure AI content, correctly reflected humanized content, produced the lowest false positive rate, and most importantly showed exactly which sentences were flagged. That sentence-level transparency is what makes it genuinely useful for writers, educators, and SEO professionals.

Copyleaks also performed well, particularly on raw AI content. Its detailed percentage breakdowns make it a solid choice for content teams managing large volumes.

Grammarly detected obvious, unedited AI content reliably. But it failed on humanized content, produced high false positives on human writing, gave inconsistent scores on different days, and provided no sentence-level detail. For casual writing assistance, Grammarly remains excellent. As a dedicated AI detector, it falls short.

Conclusion

Grammarly's AI checker is a convenient bonus feature for existing Grammarly users. If you already pay for Grammarly Premium for its grammar, style, and plagiarism tools, the AI detection is a useful quick check as long as you treat the result as a rough estimate, not a reliable verdict.

However, if your primary need is accurate AI detection for academic integrity, content publishing, SEO verification, or professional screening Grammarly is not the right tool. Its inconsistent scoring, high false positive rate, and complete lack of sentence-level transparency make it unsuitable for high-stakes use.

For reliable AI detection, AI Checker delivers significantly better accuracy, clear sentence-level analysis, and a free tier that requires no account. It is built specifically for the job Grammarly's AI checker only partially does.

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