Scribbr AI Detector Review: How Accurate Is It Really?

AI writing has become almost impossible to ignore, and with it comes a wave of AI detectors.

Scribbr, best known for academic proofreading, now offers its own AI detection tool.

But how reliable is it really? In this review, you’ll see how it performs in real tests, what features it offers, and whether it can truly catch AI-generated text.

What is Scribbr?

Scribbr is a platform that began as a proofreading and writing assistance service, primarily helping students improve academic work. Now owned by Learneo (formerly Course Hero), Scribbr has expanded its offerings to include tools for plagiarism detection, AI detection, grammar checking, and citation generation, making it a comprehensive resource for students, writers, and educators.

What is Scribbr AI Detector?

Scribbr AI Detector is a free tool, powered by QuillBot’s detection engine, that identifies whether text is human-written, AI-generated, or AI-refined. It is designed to help maintain academic integrity and ensure originality across documents.

Core Functions:

• AI Text Detection: Identifies text generated by AI models like ChatGPT, Gemini, and Copilot.

• Mixed-Content Detection: Distinguishes between fully human-written, AI-generated, or AI-refined passages.

• Sentence & Paragraph Analysis: Highlights specific sections of text likely written by AI.

• Supported Formats: Paste text, upload documents (DOCX, PDF, TXT), or use via API integration.

• Multilingual Support: Detects content in multiple languages, including English, German, French, and Spanish.
  
  

How Accurate is Scribbr AI Detector?

Scribbr officially claims its AI detector is trained to identify text from popular models like ChatGPT, Gemini, and Copilot with high accuracy, even differentiating between human-written, AI-generated, and AI-refined content. However, like most AI checkers, Scribbr also notes that no tool can guarantee 100% accuracy. To evaluate this claim, we ran three controlled tests: one on fully AI-generated text, one on mixed human–AI writing, and one on humanized AI text.

Test 1: Pure AI Text

Setup: We generated a 100% AI-written passage using ChatGPT-5. This ensures the text has no human contribution and serves as a baseline for Scribbr’s detection ability.

Results: Scribbr AI Detector flagged 97% of the text as likely AI and 3% as human-written.

scribbr-ai-detector-checks-pure-ai-text-results 

Observations: This result is consistent with expectations and shows Scribbr’s detector is effective at identifying purely AI-generated writing. While not a perfect 100%, the high score demonstrates reliable detection of machine-written content.

Test 2: Mixed AI + Human Writing

Setup: We used a human-written academic paragraph (written before the release of ChatGPT) and asked ChatGPT-5 to continue the text. The final passage contained 187 human-written words (41%) out of 454 total words.

Results: Scribbr AI Detector identified:

• 44% of text as likely AI

• 6% as human-written & AI-refined

• 50% as human-written

scribbr-checks-mixed-ai-and-human-writing-results 

Observations: The tool performed reasonably well, recognizing the presence of both human and AI input. However, the proportion of AI-detected text was slightly lower than the actual 59%, showing that Scribbr may under-report AI involvement in mixed texts.

Test 3: Humanized AI Text (QuillBot)

Setup: We took the 100% AI text from Test 1 and ran it through QuillBot’s AI Humanizer in advanced mode, which rewrites content to appear more human-like.

Results: Scribbr AI Detector flagged the text as 100% likely AI.

scribbr-checks-quillbot-humanized-text-results.webp

Observations:

This indicates that Scribbr’s detector was not fooled by QuillBot’s humanization attempt. While this could suggest strong resistance to simple paraphrasing tools, it may also reflect an overly rigid detection method that risks false positives in cases of heavily edited text.

Scribbr AI Detector Pros and Cons

Like most AI checkers, Scribbr’s detector has strengths and weaknesses. Based on our tests, user feedback, and comparisons with QuillBot’s AI Detector, here’s a balanced overview:

Pros ✅

• Consistent results with QuillBot: Since Scribbr uses QuillBot’s backend, the detection outcomes align with what we found in our QuillBot review.

• High accuracy in detecting AI text: Performs well in identifying fully AI-generated writing.

• Ease of use: The interface is clean, simple, and easy to navigate.

• Generous free plan: Allows unlimited free AI checks with a word cap per submission, making it practical for frequent use.

• Multilingual support: Can analyze texts in several major languages (e.g., German, French, Spanish).

Cons 

• False positives: Human-written work may be mistakenly flagged as AI-generated or AI-refined.

• Limited transparency: It doesn’t explain how detection scores are calculated in detail.

• Limited feedback: Highlights AI-like sentences but does not provide deeper analysis or revision suggestions.

• Plagiarism accuracy issues: Some plagiarism results may be inaccurate or miss relevant matches.

• High cost for advanced tools: While the basic AI detector is free, more advanced Scribbr services (plagiarism check, proofreading) can be expensive.

Scribbr AI Detector Pricing

Scribbr’s AI detector is completely free to use, with a limit of 1,200 words per submission and unlimited checks. No sign-up is required, making it accessible for quick analysis.

However, Scribbr itself does not offer a premium upgrade for its AI detector. If you want advanced features such as higher word limits, more detailed detection, or integration with other tools, you’ll need a QuillBot Premium membership, since Scribbr’s detector runs on QuillBot’s backend. QuillBot’s paid plans are billed separately and not included under Scribbr.

https://www.essaydone.ai/images/article/ai-detector/quillbot-pricing.webp 

Can You Bypass Scribbr AI Detector?

While Scribbr’s AI detector is effective at flagging AI-generated content, it is not foolproof. For students, researchers, or professionals who rely on AI tools, bypassing detection can become a necessity—especially when detectors mistakenly classify original human work as AI-generated. However, achieving this is not simple.

Basic rewriting or word-swapping often fails. For example, in our test with QuillBot’s humanizer (Test 3), Scribbr still marked the text as 100% AI-generated. This shows that simple paraphrasing tools cannot reliably fool the detector.

A more advanced solution is EssayDone Humanizer, which rewrites text at a deeper linguistic and structural level. Unlike basic paraphrasers, it adjusts sentence flow, grammar, and natural variation—making the writing appear genuinely human.

Why does this work? Because Scribbr’s detector analyzes patterns, sentence structures, and statistical word choices. When these patterns are meaningfully altered, the text loses the telltale “AI footprint.” In practice, when we ran the 100% AI-generated text from Test 1 through EssayDone Humanizer, the AI score dropped to 0% AI, while keeping the content clear and natural.

Scribbr-check-essaydone-humanized-text-0-percent-ai 

5 Alternatives to Scribbr AI Detector 

FAQ

Is Scribbr AI detector 100% accurate?
No. Scribbr itself acknowledges that no AI detector can be 100% accurate. While it can identify many AI-generated patterns, false positives and missed detections are still possible.

How to bypass Scribbr AI detector?
Basic rewriting or paraphrasing is usually ineffective, as seen in our tests. More advanced humanization tools are needed if the goal is to avoid being flagged.

Will my professor use an AI detector?
Many professors and institutions now use AI detectors, including Scribbr or similar tools, especially in academic settings. However, the choice varies by school or instructor.

Can I use AI detectors on my own work before submission?
Yes. Many students use tools like Scribbr to check their work and ensure it will not be flagged as AI-written before submitting.

Are AI detectors legal?
Yes. Using AI detectors is legal, but how their results are applied depends on institutional or workplace policies.

Is Scribbr AI detector free?
Yes. Scribbr offers a free version that allows up to 1,200 words per submission without requiring an account. For advanced features, users need a QuillBot premium subscription.

Conclusion

In this review, you’ve seen what Scribbr is, how its AI detector works, and how accurate it can be when tested against pure AI, mixed writing, and humanized text. 

We also covered its pros and cons, pricing, and common questions that many users have. While no AI detector is flawless, Scribbr provides a useful case study in how these tools function. Hopefully, this article gives you clarity and helps you better evaluate AI detection tools.