Identifier utility
Batch CAS number checker
Check number format, verify checksums and find matching records.
Paste your CAS numbers
What the check tells you
Format
Checks the three hyphen-separated groups and digit lengths.
Check digit
Verifies the weighted checksum of the preceding digits.
Catalog match
Looks for the number among the 1,000 records in this release.
A passed checksum is not proof that a number has been assigned by CAS. Absence from this catalog does not mean a number is invalid.
CAS check-digit documentation ↗