Definition:
If a release it is chart eligible, it means that it meets the requirements to be considered for placement in the music charts. Chart eligibility rules differ from country to country, and there are different requirements for different kinds of releases. Chart eligibility in one country does not imply chart eligibility in another.
Some things that may impact chart eligibility is how many tracks is on the album, whether or not it has a barcode, how many b-sides are on a single and how long the release is.
