Non-resolving DOIs
DOIs that lead to broken links or missing records in Crossref and OpenAlex.
Free reference and citation checker
Paste your bibliography or upload a PDF. Cross-reference every DOI, author, and year against Crossref, OpenAlex, and arXiv in two minutes.
Check your referencesFree to start. No credit card required.
- Databases
- Crossref, OpenAlex & arXiv direct API lookup
- Turnaround
- Under two minutes
- Price
- Free on every plan (no credits used)
What the reference checker catches
Mismatched papers
DOIs that resolve to completely different publications than the cited title.
Discrepant metadata
Titles, publication years, or author orders that differ from the published record.
Unverified citations
Entries with no matching record anywhere, including AI-hallucinated citations.
Missing DOIs
Suggests official DOIs for valid publications cited without one.
Preprint updates
Identifies preprints that have since been published in peer-reviewed journals.
How citation verification works
- 1
Paste or upload
Paste formatted citations or upload your manuscript PDF to extract the bibliography.
- 2
Direct index resolution
Resolve DOIs and arXiv IDs directly; search remaining titles via OpenAlex.
- 3
Metadata comparison
Compare title, year, volume, and first author against canonical publisher records.
- 4
Audit report
Color-coded summary: Verified, Metadata Differs, Wrong Work, or Not Found.
Who it is for
- Authors verifying bibliographies before journal or conference submission
- Graduate students checking citations in master’s and doctoral theses
- Researchers auditing AI-assisted citation drafts for hallucinations
- Editors and peer reviewers screening manuscript bibliographies
Scientific integrity boundaries
- Pure deterministic database lookup; zero language models involved.
- Books, software, and web pages are less indexed and may require manual inspection.
- Verifies citation existence and accuracy; does not evaluate contextual relevance.
Questions
How does it verify citations?
It queries bibliographic databases directly and compares title, year, and authors with what was actually published.
Can it detect citations made up by AI assistants?
Yes. Fabricated citations typically fail to resolve in Crossref or OpenAlex, or have mismatched authors and years, which our checker flags immediately.
Is the reference checker really free?
Yes. Reference checks do not use language model inference, so they are free on every plan, up to 50 a month.
Which citation styles are supported?
Numbered lists, APA, Harvard, Chicago, and Vancouver. Paste your formatted list or upload your PDF.
Do I need to upload the entire paper?
No. You can paste just your bibliography section, or upload the PDF for automatic extraction.