Free Duplicate Publication Checker for Academic Papers

What it checks

Eight independent sources, two retrieval strategies. Title-fuzzy matching catches near-identical titles (token-set ratio ≥ 0.6 plus n-gram overlap). Abstract-fuzzy matching catches the case where the title was rewritten between submissions but the underlying study is the same — common in salami-sliced papers where a single dataset is split into three publications.

For every flagged match we return: the matching paper's title, DOI or preprint ID, journal/server name, year, similarity score, and a short rationale. You decide whether each match is a true duplicate (rejection risk), a legitimate self-citation (cite it), a related-but-distinct work (cite it as related), or a false positive.

• CrossRef — 1.4M journals, 130M+ DOI-assigned articles
• arXiv — physics, math, CS, quantitative biology preprints
• medRxiv — medical preprints (clinical, public health, RCTs)
• bioRxiv — biology preprints (genomics, neuroscience, ecology)
• Unpaywall — open-access version index covering 50M+ articles
• Our 900,000-paper institutional library (EBSCO, OpenAlex, KKU)
• Pre-press registrations from venues that share metadata
• Cross-reference: the manuscript's own citation list (catches the 'forgot you already published this' case)

How it works (5 steps)

The full check runs as part of our free Pre-Check tool. No signup, no upload, just paste-and-submit.

• Step 1. Paste your title and abstract — Open the Pre-Check tool, paste the working title and abstract of the manuscript you want to check.
• Step 2. CrossRef scan (1.4M+ journals) — We cross-reference your title against CrossRef's full registry of DOI-assigned articles, scoring matches by token overlap and fuzzy similarity.
• Step 3. Preprint scan (arXiv, medRxiv, bioRxiv) — Parallel scan of the three largest preprint servers in physics/CS, medicine, and biology. Catches the case where you posted a preprint and forgot, or where a co-author posted without telling you.
• Step 4. Unpaywall + institutional library scan — Unpaywall covers open-access copies; our 900K-paper KKU institutional library covers paywalled cohorts that aren't in CrossRef. Together they catch grey-literature duplicates and conference proceedings.
• Step 5. Confidence score + flagged matches — We return a 0-100 confidence score per match, plus the matching title, DOI/URL, and overlap percentage. You decide what's a true duplicate, a legitimate self-citation, or unrelated.

Why it matters (the editorial reality)

Three failure modes that this check exists to catch:

Salami slicing — splitting one study into the 'least publishable units' to inflate publication count. Reviewers detect it, editors reject for it, and the COPE (Committee on Publication Ethics) flowchart for handling it is explicit. Our checker finds the upstream parts before they catch you.

Forgotten preprint — you posted a working draft to arXiv or bioRxiv 18 months ago, your advisor encouraged you to develop it further, and now you're submitting the polished version. Most journals are fine with this if disclosed. Some aren't. Either way, the editor will check, and you should know what they'll find before they find it.

Multi-language re-publication — a paper published in Turkish, Chinese, or Spanish translated and resubmitted to an English-language journal is one of the most-cited retraction causes in the 2010-2025 retraction-watch dataset. Our library coverage includes non-English venues that traditional checks miss.

When to use it

Four moments in the submission cycle where running this check is high-leverage:

• Pre-submission, after the manuscript is ~80% done — gives time to add a citation or restructure if a match surfaces.
• Before resubmitting to a second venue after a rejection — the previous submission may have been indexed.
• Before responding to a reviewer's prior-publication concern — bring receipts. A confidence score is more persuasive than 'we don't think so'.
• When taking over a co-authored manuscript from a lab member who has left — catches the 'silent submission' case where a former co-author posted to a preprint server without telling the group.

What we DON'T do

Explicit limitations, because false confidence is worse than known gaps:

• Not a full-text plagiarism scanner. We match titles and abstracts, not body paragraphs. If a paper paraphrases your entire methods section, we won't catch it.
• Not iThenticate / Turnitin / Crossref Similarity Check. Those are body-text similarity tools that journals run internally; we're complementary to (not a replacement for) them.
• Not a substitute for institutional integrity review. If a match surfaces and you're unsure, talk to your research office.
• We don't store your manuscript. Title + abstract are POSTed to our API, scanned in-memory, and discarded — no DB write. Zero retention.
• Confidence scores are bounded by source coverage. If a duplicate exists in a venue we don't index (some predatory journals, some non-OA paywalled non-CrossRef-deposited journals), we will miss it.

Is it really free?

Yes. The duplicate check is bundled into our free Pre-Check tool — no signup, no rate-limit beyond a reasonable per-IP throttle, no upsell. We make money on the optional AI Review service ($10 single, $15/mo unlimited) for the full peer-review report on your PDF; the Pre-Check + duplicate check are free standalones we publish to seed trust.

If you find a duplicate via our tool, that's the entire value — we hope you remember us when you're choosing a peer-review service. No payment, ever, for the duplicate check.

Frequently asked questions