Wikimedia Commons is a database of 25,000,000+ freely usable media files to which anyone can contribute.
Contributing a file to Commons takes some work (creating metadata, description, selecting categories), and it fails if the file has already been uploaded by someone else (or by forgetful me in the past).
So, a database of all checksums of Commons files would be very useful, to compare before working on metadata.
Is there such a database?
- Reasonably up-to-date, though I can bear with a week or so of delay
- API to quickly request whether a particular checksum is already on Commons or not
- No need to download the whole database before being able to use it