Free UDI decoder and GTIN check digit validator
Paste a GS1 UDI string and see it parsed in real time — Application Identifiers decoded, GTIN-14 check digit verified, date formats validated. No account, nothing uploaded, free to use.
What the decoder checks
- Application Identifier structure — (01) GTIN, (10) lot or batch, (11) production date, (17) expiration date, (21) serial number, (240) additional product ID, (30) variable count
- GTIN-14 check digit — computed with the mod-10 algorithm and compared against the digit you supplied
- Date formats — YYMMDD validation, including the day-00 end-of-month convention and impossible dates like month 13
- Field lengths — fixed-length AIs that are the wrong size, and variable-length AIs that exceed their maximum
- Unknown AIs — flagged rather than silently ignored
How the GTIN-14 check digit works
A GTIN-14 ends in a check digit calculated from the preceding thirteen. Multiply those digits alternately by 3 and 1, starting with 3 at the leftmost position. Sum the results. The check digit is whatever value brings that sum up to the next multiple of ten.
Worked example using 00199284962699: the weighted sum of the first thirteen digits is 141, the next multiple of ten is 150, so the check digit is 9 — which matches. The string is valid.
This matters because a failing check digit is rejected at the registry before anyone assesses the content of your submission, and because a scanner in a hospital will simply refuse to read it.
Reading a UDI by hand
Take (01)00199284962699(10)A2204(11)260112(17)271231. That is a device identified by GTIN 00199284962699, from lot A2204, produced on 12 January 2026, expiring 31 December 2027. The parenthesised numbers are the Application Identifiers telling the scanner what each field means.
The DI portion — the (01) — is what registries like GUDID and EUDAMED key on. The rest is production data that varies unit to unit.
Other free tools on this site
- Label checker — paste label text or drop a file and get a severity-ranked compliance report. Runs entirely in your browser; files are never uploaded.
- Compliance plan generator — select device class and target markets, get a phased implementation plan.
- UDI readiness assessment — six questions, a score out of 100, and the specific gaps that registries and auditors reject on.
- UDI AI assistant — ask regulatory questions and get answers grounded in current requirements.
All of them are free and require no account. They exist because a genuinely useful tool is a better introduction to a consultancy than a brochure.
A note on limits
The decoder validates syntax and check digits. It cannot see print quality, symbol grading, or physical placement on the device, and a clean parse is not a compliance certification. Pair it with human verification before any release decision.
Talk to a UDI consultant
Scoping conversations are free and usually take thirty minutes. Tell us what you make, where you sell it, and where UDI hurts.