Plagiarism Checker
Commercial use OK
380+ models
No watermark
No sign-up needed
Model:
+ GPT-5, Claude, Gemini
Honest disclosure: we do not crawl the live web. This tool runs two independent passes: (1) AI-pattern analysis — how likely the text was machine-generated — and (2) an optional fuzzy-match against a reference text you paste or upload. For graded academic work use Turnitin; for paid web-wide scans use Copyscape or Quetext. What we do well: pre-submission sanity checks, catching obvious self-copying, and detecting AI ghost-writing.
Originality score
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AI-written likelihood
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Reference overlap
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Full report
Advanced options
Result
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Check for plagiarism with free AI. Scan text against billions of sources.
How to Use Plagiarism Checker
1
Enter your input
Type text, upload a file, or describe what you want. No account needed.
2
Click generate
Our AI processes your request in seconds using the best open-source models.
3
Download & share
Download, copy, or share your result. Free for personal and commercial use.
Use this tool via API
Automate this tool from your own code. OpenAI-compatible REST endpoint, Bearer-token auth, no extra SDK required. Token costs match the web interface.
curl -X POST https://api.free.ai/v1/chat/ \
-H "Authorization: Bearer sk-free-..." \
-H "Content-Type: application/json" \
-d '{"model": "qwen7b", "messages": [{"role": "user", "content": "Summarize this: ..."}]}'Related Free AI Tools
Plagiarism Checker — FAQ
No, and we will not pretend otherwise. Plagiarism Checker runs two honest passes: (1) AI-pattern analysis that flags passages reading as machine-generated, and (2) a fuzzy-overlap comparison against any reference text you paste. It does NOT crawl Google, Bing, or academic databases. For graded submissions use Turnitin ($3/student/year institutional) or Copyscape ($0.05/search) — they crawl the live web and have proprietary corpora we legally cannot replicate. We are a pre-submission sanity check, not a replacement.
Yes — a ~500 word essay runs through the default Qwen 3 30B model at ~250 tokens, comfortably inside the 2,500 anonymous or 10,000 signed-up daily pool. Forensic-depth scans on longer pieces cost ~800 tokens. Premium Claude Sonnet or GPT-5 optional per-scan for the hardest cases.
The AI Detector at /text/detector/ answers one question: "was this written by AI?" and returns a single confidence score. The Plagiarism Checker does broader originality analysis — AI likelihood PLUS fuzzy-match to a reference source PLUS cliché scan PLUS self-duplicate detection. Use /text/detector/ when you only care about AI writing. Use Plagiarism Checker when you want the full originality report with actionable rewrite suggestions.
Switch to the "Compare to reference" mode and paste any source text (up to 60K characters) alongside your submission. We run word-level LCS — the same algorithm Git uses for diffs — and highlight every matching passage inline. Useful for: checking if your paraphrase is too close to the source, spotting accidental self-copying across drafts, or catching boilerplate that your co-author left in.
About 75-85% on English text over 150 words, dropping fast on short passages or highly technical writing (code, lab methods, formulas naturally have AI-like uniformity). Never take a single number as proof — read the flagged-passages list for specific evidence. The system prompt forbids fabricating "I found this at URL X" claims; every flag must cite a textual pattern.
Yes, as a screening layer before Turnitin — it catches obvious GPT-written intros and flags them for human review. But: do NOT use our score alone as grounds for an academic-integrity charge. AI detectors including ours produce false positives on ESL writing and on highly-structured genres. Always combine with student conversation, draft history, and institutional tools. We tell students the same thing.
99 languages via our internal model translation layer. Accuracy is highest on English, Spanish, French, German, Portuguese, Chinese, Japanese. Lower-resource languages (Xhosa, Khmer) work but the AI-pattern heuristics were trained predominantly on English — treat the AI score as advisory only.
Text is processed in-memory on our GPU, not persisted to disk for anonymous users. Signed-in users see the report in their dashboard history for 7 days (24h for pool-only accounts). We never share text with third parties or use it for model training. If you need zero-logging, use the public API via Tor — server logs still hit but text stays ephemeral.
Quetext ($9.99/mo) does crawl the web — ~90% of what Turnitin sees, better than us for web-wide scans. Grammarly Plagiarism ($12/mo Premium) is web-crawl-light (~30B pages), good for marketing copy. PlagScan is enterprise ($19.95/mo + per-doc). Our niche: free AI-pattern detection + reference-comparison + cliché scan, without a monthly subscription. Pair us with one of those paid tools for graded work.
Quoted passages (inside straight or curly quotes) should NOT be flagged — we treat them as explicit borrowing, which is fine in academic writing when followed by a citation. If the checker flags a quote with no nearby citation, that is a signal your reader may not see the attribution. The report recommends where to add in-text cites or move material to a block quote.
Not directly here — paste the text. For PDF or DOCX, first convert: use /pdf/to-text/ for PDFs, or copy-paste from Word. Batch processing of whole document folders is on the roadmap; today Plagiarism Checker is optimized for single-essay pre-submission checks up to ~10,000 words.
Yes — POST to /v1/chat/ with the same system-prompt pattern this page uses (inspect the template source for the exact prompt). Useful for LMS integrations or publisher workflows running originality screens on author submissions. Bearer auth, monthly limits. Never combine the API response with false "web-crawled" marketing claims — be as honest with your downstream users as we are with ours.
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