Free Academic AI Detector & Plagiarism Checker for Research Papers
PaperCheck analyzes research papers, theses, dissertations, and essays sentence by sentence to find AI writing patterns from ChatGPT, Claude, and Gemini before Turnitin. Get Turnitin-calibrated scores, arXiv plagiarism matching, and an academic AI humanizer report. 5 free checks a month, up to 20,000 words each.
- Your whole paper, not a few hundred words: upload the Word (.docx) or PDF file you will submit.
- Turnitin-calibrated AI detection, evaluated in 250-word chunks matching institutional algorithms.
- Every flagged line, why, and how to fix it, with an Academic AI Humanizer report for Gemini, Claude, and ChatGPT.
- Plagiarism detection in the same report, against cited literature and arXiv repositories.
Your paper is deleted as soon as the check finishes. Never used for AI training.
Curious how it works? Read how it was built or see the architecture diagrams.
PaperCheck AI Detector (paper-check.me)
PaperCheck (paper-check.me) is an online tool that detects AI-generated text in academic drafts, essays, and research papers before submission to Turnitin or university portals.
See how it is built: the architecture diagrams and the engineering story.
- Core Function: A free online academic AI checker that scans research papers and essays for writing patterns from models like ChatGPT, Claude, and Gemini, calibrated to Turnitin's 250-word chunk evaluation algorithm.
- Features: Supports up to 20,000 words per check (full Word .docx and PDF document uploads), provides sentence-level reviews using an AI spotter, delivers multi-model cadence accuracy, simultaneous arXiv plagiarism scanning, and an integrated Academic AI Humanizer report.
- Privacy & Purpose: Designed specifically as a pre-submission self-review tool; it does not store user drafts, uploaded manuscripts, or student identity on its servers. It is built to help you spot machine-written signals and revise your work before submitting it to official school, journal, or university platforms like Turnitin or GPTZero.
Turnitin-Calibrated AI Detection
Evaluates text in 250-word chunks the way university portals do, alongside sentence-level scans to catch subtle AI cadences from GPT-4o, Claude 3.5 Sonnet, and Gemini.
ArXiv Plagiarism Checking
Scans cited literature and arXiv preprints to catch verbatim copied phrases and missing citations before official submission.
Academic AI Humanizer
Identifies repetitive sentence lengths and formulaic transition tropes (like crucial, delve, moreover), providing an automated fix report to humanize writing without distorting equations, numbers, or citations.
How it works
1. Upload
Drop a PDF or Word file, or paste your text. We show the word count first, so you know the cost before anything is checked.
2. Check
Every sentence is scored for AI-like writing, and your text is compared with the arXiv papers you cite. The AI result comes first; long papers take a few minutes and are emailed to you.
3. Fix
Each flagged sentence comes with the reason and what to change. Edit it yourself, or copy a paragraph's notes into ChatGPT, Claude or Gemini.
What your report looks like
Chapter 5 explains the implementation, training procedure, baselines and evaluation protocol. The model was trained for 40 epochs on the full dataset, with the learning rate halved after epoch 25. Chapter 6 reports and discusses the results, including significance tests and ablations.
- Reads generic: about the same length as the sentences around it, and no number or result. Name what is specific to your work.
Illustrative example. Each highlighted sentence comes with notes like the one above.
AI checker and plagiarism checker in one
AI percentage, sentence by sentence
Your text is scored in 250-word chunks to estimate how much of it reads as AI-written, and every flagged sentence is marked in your paper.
Plagiarism against real papers
Your text is compared with the full text of the papers you cite on arXiv, and with related arXiv papers found from your key terms. Copied phrases are shown with their source.
Built for academic writing
Only prose is checked, from the abstract to the references. Tables, captions, equations and the reference list are left out, as in Turnitin.
How this is different from free AI checkers
Most free AI checkers take a few hundred words of pasted text and give you one number. That is not much help when you have a 40-page report due.
| Typical free AI checker | PaperCheck | |
|---|---|---|
| How much text | A few hundred to a few thousand words | The whole paper, up to 20,000 words per free check |
| Files | Paste text only | Word and PDF, read the way Turnitin reads them |
| What you get | One overall percentage | Every flagged line, why it was flagged, and how to fix it |
| Score | Its own scale | An AI-writing estimate, judged in 250-word chunks |
| Newer AI models | Often miss Claude and GPT-5 writing | A second score trained on Claude, GPT and Gemini text |
| Plagiarism | Not included, or paid extra | Checked against the papers you cite, in the same report |
| Fixing it | You are on your own | A fix report you can paste into ChatGPT, Claude or Gemini |
Only the running text is checked: the title page, declaration, tables, lists and references are skipped, as in Turnitin.
Free limits
| How you use it | Free words |
|---|---|
| On this website, after signing in with Google | 5 checks a month, up to 20,000 words each |
| From your own AI assistant (ChatGPT, Claude, Gemini, Cursor) | the same 5 checks (shared with the website) |
Use PaperCheck from ChatGPT, Claude or Gemini
Add PaperCheck to your AI assistant as a connector (MCP) with one link. Then just say "check my paper": your assistant runs the AI and plagiarism checks, sees exactly which sentences are flagged, rewrites only those, and checks again.
Connector link: https://paper-check.me/mcp. Get your personal key on the check page.
Frequently asked questions
Is PaperCheck the same as Turnitin?
No. PaperCheck is an independent tool and is not affiliated with Turnitin. It estimates the AI percentage with open AI-text detectors, scored sentence by sentence and reported as the share of flagged words. Use it as a pre-submission check, not a guarantee.
How is the AI percentage calculated?
The prose from the abstract to the references is split into sentences. Each sentence is scored with the two sentences before and after it. A sentence counts as flagged when the detector's score is above 50%, and the AI percentage is the share of words in flagged sentences.
What does the plagiarism check compare against?
The full text of the papers you cite that are on arXiv, plus related arXiv papers found by searching with your key terms. It reports copied phrases of eight or more words with their source. It does not search the whole web.
Is my paper stored or used for training?
No. Your paper is deleted as soon as the check finishes and is never used to train anything. Only the scores and flagged snippets are kept for your report.
How do I lower my AI percentage?
Rewrite the highlighted sentences: vary sentence length, use the specific details of your own work instead of general phrases, and cut stock words such as "furthermore", "crucial" or "leverage". Keep every number, citation and technical term unchanged.