Canadian · Validation
DOI checker & validator.
Paste a DOI, a doi.org link or a doi: reference to check its syntax and get a normalized DOI and a doi.org link. This checks syntax only: a DOI has no check digit, and this tool cannot confirm the DOI is registered or that it resolves. Everything runs in your browser: nothing you type is transmitted anywhere.
Inputs
Result
Enter a DOI and press Check DOI.
How DOI syntax is checked
A DOI name is a prefix and a suffix separated by a slash. The prefix is the directory indicator, usually 10, a full stop, and a registrant code of digits. The suffix is chosen by the registrant. Unlike an ISBN or ISIN, a DOI has no check digit, so there is nothing to compute: this tool can only test whether the text is shaped like a DOI.
The primary test is the pattern Crossref recommends for modern DOIs: /^10\.\d{4,9}\/[-._;()/:A-Z0-9]+$/i. Crossref reports it matches 74.4 million of the 74.9 million DOIs it has seen. We escape the prefix dot so it must be a literal full stop. Matching is case-insensitive because DOI names compare case-insensitively over the Basic Latin letters (Handbook section 4.3.4), so the normalized DOI is shown in lowercase.
Some older DOIs, mostly early Wiley identifiers such as 10.1002/(SICI)1097-4571(199806)49:8<693::AID-ASI4>3.0.CO;2-O, are legal under the DOI Handbook but fall outside that pattern. The tool tells those apart from input that is not a DOI at all.
Sources: Crossref, DOIs and matching regular expressions and The DOI Handbook (ISO 26324), section 4.3.
What a passing check does and doesn’t tell you
This tool checks syntax only. A DOI that passes is correctly formed; it may still be unregistered, mistyped into a different real DOI, or retired. To confirm a DOI resolves, open the doi.org link it produces. This tool makes no lookup: it runs entirely in your browser, and nothing you type is transmitted, stored, or logged.