ISWC - International Standard Musical Work Code

What is ISWC?

ISWC is a universal unique and unambiguous identifier of a musical work.


There are so many musical works being created daily by many people. Neither titles nor names of authors are unique. “Love by John Smith” says almost nothing. Both the author and the work must be precisely identified. This is what identifiers do.

Any good global identifier must be:


This is explained in detail in the following, very technical video, part of my series about the potential use of blockchain tech in music rights. Issuing ISWC

In order to identify a musical work, the ISWC authority, who actually issue ISWCs, uses the following data:

work title
ALL authors with their IDs and their roles

There may be multiple works where this data is the same. The details are beyond this article, but this is handled as well, though not elegantly.

One can only get an ISWC through a collecting society (PRO, MRO, CMO, etc.), contacting the ISWC authority directly is not possible. This is the cause of the misconception that societies issue ISWCs.

Another common conception is that publishers issue them. This is caused by the fact that ISWC is compared to ISRC, the recording identifiers. These two identifiers are very different in many ways, although the names are very similar. Once again, see the video about Identifiers linked above.

More on requesting ISWCs can be found in the video linked below. ISWC Format and Validation

ISWC format is a letter, followed by 10 digits. The letter is T, but other letters may be used in the future. The first 9 digits are the actual number, and the last one is a checksum digit. If you are interested in the algorithm, check from my Django-Music-Publisher project,

There are three different ways one ISWC can be written.:


Please note that the same format is used for IPI base numbers, except that the leading letter is I, not T. IPI name and base numbers are covered in this article.