VerlumoAIAI search assistant that answers questions with cited sources.
View detailsCrossref
Registry that links scholarly content with persistent DOI identifiers.
Crossref is a registry that links scholarly content with persistent DOI identifiers. When a publisher registers a paper, Crossref assigns it a DOI — a permanent link that never breaks — and stores its metadata: title, authors, journal, and references. It is the infrastructure behind academic citations, used by publishers, libraries, and researchers worldwide.
Key Features
- Free DOI lookup for any scholarly work
- Metadata for millions of papers, books, and datasets
- Citation linking between works
- Free API for developers and publishers
- Reference checking and validation
- No account needed
Pricing
| Plan | Price | Details |
|---|---|---|
| Free | $0 | DOI lookup, metadata, and API access — no payment required. |
Prices as listed in 2026 research. Always check the official site for the latest price — plans change. Free plan: Yes — it has a free plan.
Best for: anyone who needs to find, link, or cite a paper by its DOI.
Popular with: Students, Teachers, Developers
Popular with: Students, Teachers, Developers
How it works
The service is free for anyone to search, with no account needed. You can look up any DOI to find a paper's metadata, resolve a citation, or check whether a reference is correct. It also offers a free API for developers who build citation tools.
Crossref is not a search engine or a reading tool — it is the registry that makes citations work. For anyone who needs to find a paper by its DOI, verify a reference, or build a tool that uses citation data, it is the authoritative source.
Pros and Cons
✓ Pros
- Authoritative source for DOI and citation data
- Completely free with no account needed
- Free API for building citation tools
- Used by publishers worldwide
✗ Cons
- A registry, not a search engine — no full-text search
- Interface is built for publishers and developers
- No AI features or reading tools
Frequently Asked Questions
Is Crossref free?
Yes — Crossref has a free plan. Free
What is Crossref best for?
anyone who needs to find, link, or cite a paper by its DOI.
What kind of tool is Crossref?
Crossref is a Research Tools tool on VerlumoAI.
Related Tools
AI research assistant that answers questions from 138M+ academic papers.
View detailsGoogle's source-grounded research assistant — ask your documents, get cited answers.
View detailsLast reviewed: November 2026