Top 14 AI Plagiarism Checkers To Spot ChatGPT Content in 2025

GPTZero is a favorite for catching AI text. It checks how predictable words are to decide if a human or AI wrote them. The interface is simple, and results are clear.

It rarely mistakes human text for AI, though it happened once in our tests. It’s great for quick scans and gives detailed metrics like perplexity. You can start using it for free.

• Accuracy: 99% overall, with 2% false negatives and 1% false positives (verified via GPTZero’s site).
• Free Available: Yes, free with an account for longer texts.
• Starting Price: Not specified; premium plans exist but pricing isn’t public.
• Document Types: Supports text paste, file uploads (PDF, DOCX); works in English, German, French, Spanish, Portuguese.

Try GPT Zero→

Copyleaks boasts a 99.12% accuracy rate. It supports multiple languages like Spanish and German. The tool uses AI to stay ahead of new chatbots.

We tested it with a 600-word article from a tech site. It took 10 seconds to confirm it was human-written. There’s also a Chrome extension for easy checks.

• Accuracy: 99.12%, with 0.2% false positives (Copyleaks’ official claim).
• Free Available: Yes, up to 2,000 words monthly with free credits.
• Starting Price: $16.99/month for Personal plan (verified on Copyleaks’ pricing page).
• Document Types: Text (255 characters to 2,000 pages), source code; supports 30+ languages.

Try Copyleaks→

Writer AI is known for its writing tools, but its detector shines too. You paste text or a URL, and it checks up to 1,500 characters. It’s simple and effective.

In our tests, it easily spotted AI text versus human work. For big texts, split them into parts. It’s free, making it great for casual users.

• Accuracy: Not specified, but reliable in tests with clear AI-human distinction.
• Free Available: Yes, up to 5,000 words (confirmed on Writer’s site).
• Starting Price: Not listed; contact for enterprise plans.
• Document Types: Text inputs, URLs; primarily English.

Try Writer AI Content Detector→

Crossplag targets student assignments. It handles 1,000 words at a time and uses a strong model trained on OpenAI data. It’s still in testing but works fast.

We mixed human and AI text, and it gave a 4% AI score, which was accurate. It’s English-only for now but plans to expand.

• Accuracy: High, trained on 1.5 billion parameters; varies by text (Crossplag’s site).
• Free Available: Yes, fully free during testing phase.
• Starting Price: None, currently free.
• Document Types: Text inputs; supports blogs, emails, articles in English.

Try Grossplag→

ZeroGPT is a quick tool for spotting AI text. It claims to detect even GPT-4 content using deep algorithms. You can upload files or paste text.

In our tests, it caught half of a mixed GPT-4 text as AI, which is solid. It’s free and works in all languages, perfect for fast checks.

• Accuracy: Claims 98% accuracy; minimizes false results (ZeroGPT’s site).
• Free Available: Yes, fully free.
• Starting Price: Not specified; API pricing on request.
• Document Types: Text, batch files; supports all languages, plagiarism, summaries.

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Grammarly isn’t just for grammar—it checks plagiarism too. It uses AI to scan against billions of pages. Basic checks are free, but detailed stats need a paid plan.

In tests, it caught copied text and other issues. Premium starts at $12/month, unlocking full features.

• Accuracy: Checks against 16 billion pages; reliable originality score.
• Free Available: Yes, basic plagiarism check.
• Starting Price: $12/month for Premium (Grammarly’s site).
• Document Types: Essays, articles, research papers; paste or upload.

Try Grammarly→

Writefull is great for catching fake social media posts. It’s trained on diverse datasets and gives a percentage score for AI likelihood. It’s simple to use.

We tested it with a 500-word AI horror story and a news article. It correctly identified the AI text. It has a daily quota, so check often.

• Accuracy: Not specified, but effective in distinguishing AI vs. human text.
• Free Available: Yes, with an unstated daily limit.
• Starting Price: Not listed; contact for details.
• Document Types: Text inputs; primarily English.

Try Writefull GPT Detector→

GPTRadar uses GPT-3 to check text. It breaks down results by word probability, showing which parts seem AI-generated. It even flagged “Lorem Ipsum” as AI, which was odd.

You get 2,000 free tokens to start. Extra credits cost as little as $0.02 for 100 tokens. It’s good for detailed analysis.

• Accuracy: Relies on GPT-3; effective but varies by text complexity.
• Free Available: Yes, 2,000 tokens free (confirmed on GPTRadar’s site).
• Starting Price: $0.02 per 100 tokens (≈125 words).
• Document Types: Text inputs; English-focused.

Try GPTRadar→

Winston AI claims 99% accuracy for ChatGPT detection. It splits results into human, AI, and readability scores. You can upload PDFs or images too.

It’s fast, with an AI prediction map highlighting fake text. The free plan covers 2,000 words, but paid plans add more features.

• Accuracy: Claims 99% for ChatGPT detection (Winston AI’s site).
• Free Available: Yes, up to 2,000 words.
• Starting Price: $19/month for paid plans (verified online).
• Document Types: Text, PDFs, images; supports English.

Try Winston AI→

CopyScape is unique—it scans web pages for copies online. It’s great for businesses or anyone checking if their content was stolen. Just paste a URL.

It shows matching sites and copied word counts. Tests confirmed it’s accurate for web-based plagiarism. It’s free for now, but may change.

• Accuracy: Trusted for web scans; matches against billions of pages.
• Free Available: Yes, some features free (CopyScape’s site).
• Starting Price: Not specified; premium may apply later.
• Document Types: Web pages, articles; human or AI content.

Try CopyScape→

This tool uses billions of pages to predict word patterns. It’s accurate at spotting AI text and highlights predictable parts. It’s free to use.

We tested mixed text, and it correctly split AI and human parts. It’s great for blogs or essays and works with new AI models.

• Accuracy: High with NLP; not a full substitute for judgment (site claim).
• Free Available: Yes, fully free.
• Starting Price: Not specified.
• Document Types: Blogs, social posts, articles; supports GPT-4, Gemini.

Content At Scale→

Plagibot accepts Word docs and PDFs. Its friendly interface updates its database hourly. It caught most copied content in our tests, with rare errors.

Free users get 2,000 words monthly. Paid plans are available, but you’ll need to contact them for pricing details.

• Accuracy: Claims fastest and most accurate; varies by source (Plagibot’s site).
• Free Available: Yes, 2,000 words/month.
• Starting Price: Contact for pricing.
• Document Types: DOC, DOCX, TXT, RTF; all plagiarism types.

Try Plagibot→

Corrector supports all GPT models, including GPT-4. It uses context to find similarities but only allows 300 words per check. Results show a “Fake %” score.

The simple output might confuse some users. It’s free, but lacks detailed metrics compared to others.

• Accuracy: Not specified; relies on contextual analysis.
• Free Available: Yes, fully free.
• Starting Price: Not listed.
• Document Types: Text up to 300 words; English-focused.

Try Corrector App→

Sapling uses machine learning to check tokens, not words. It’s updated for new AI models like Google’s PaLM 2. Free users get 2,000 tokens.

It’s 97% accurate but may flag some human text wrongly. It’s great for quick scans or web pages via its extension.

• Accuracy: 97%+ for AI text; <3% false positives (Sapling’s site).
• Free Available: Yes, up to 2,000 characters.
• Starting Price: Contact for high-volume plans.
• Document Types: Text, PDFs, DOCX; web pages via extension.

Try Sapling AI Content Detector→