You have to prove copying to prove infringement. But because actual copying is often done in private, under US law, courts deem copying to have happened if you

You have to prove copying to prove infringement. But because actual copying is often done in private, under US law, courts deem copying to have happened if you can prove both "access" and "substantial similarity". Substantial similarity on its own isn't enough. https://en.wikipedia.org/wiki/Substantial_similarity#Substantial_similarity_in_copyright_infringement https://en.wikipedia.org/wiki/Substantial_similarity#Substan... says: > it refers to that level of similarity sufficient to prove that copying has occurred, once access has been demonstrated.