IMSLP (https://imslp.org/wiki/Main_Page), also known as the International Music Score Library Project or Petrucci Music Library, was started in 2006. The International Music Score Library Project (IMSLP), also known as the Petrucci Music Library after publisher Ottaviano Petrucci, is a subscription-based digital library of public-domain music scores. It includes public domain and licensed recordings to allow for study by ear. The project, which uses MediaWiki software, has uploaded more than 630,000 scores and 73,000 recordings of more than 195,000 works by 24,000 composers.
Information was taken from the Wikipedia article on IMSLP.