The newer global node IDs (which can be forced via the 'X-Github-Next-Global-ID' header [1]) have a prefix indicating the "type" of object delimited by an underscore, then a base64 encoded msgpack payload. For most objects it contains just a version (starting at 0) followed by the numeric "databaseId" field, but some are more complex.

For example, my GitHub user [2] has the node ID "U_kgDOAAhEkg". Users are "U_" and then the remaining data decodes to: [0, 541842] which matches the numeric ID for my user accepted by the REST API [3].

You shouldn't rely on any of this implementation of course, instead just directly query the "databaseId" field from the GraphQL API where you need interoperability. And in the other direction the REST API returns the "node_id" field for the GraphQL API.

For folks who finds this interesting, you might also like [4] which details GitHub's ETag implementation for the REST API.

[1] https://docs.github.com/en/graphql/guides/migrating-graphql-... [2] https://api.github.com/user/541842 [3] https://gchq.github.io/CyberChef/#recipe=Find_/_Replace(%7B'... [4] https://github.com/bored-engineer/github-conditional-http-tr...