Cache version is a hash [generated](https://github.com/actions/toolkit/blob/500d0b42fee2552ae9eeb5933091fe2fbf14e72d/packages/cache/src/internal/cacheHttpClient.ts#L73-L90) for a combination of compression tool used (Gzip, Zstd etc based on runner OS) and the `path` of directories being cached. If two caches have different versions, they are identified as unique caches while matching. This for example, means that a cache created on `windows-latest` runner can't be restored on `ubuntu-latest` as cache `Version`s are different.
Cache version is a hash [generated](https://github.com/actions/toolkit/blob/500d0b42fee2552ae9eeb5933091fe2fbf14e72d/packages/cache/src/internal/cacheHttpClient.ts#L73-L90) for a combination of compression tool used (Gzip, Zstd, etc. based on the runner OS) and the `path` of directories being cached. If two caches have different versions, they are identified as unique caches while matching. This for example, means that a cache created on `windows-latest` runner can't be restored on `ubuntu-latest` as cache `Version`s are different.
> Pro tip: [List caches](https://docs.github.com/en/rest/actions/cache#list-github-actions-caches-for-a-repository) API can be used to get the version of a cache. This can be helpful to troubleshoot cache miss due to version.