The biggest new feature of the Audacity 3.0 release is a new, more evolved save file format that uses the SQLite3 database to store all the data of your audio project into a single file using the .aup3 extension.
Previous Audacity versions used an .aup file format that saved projects as a large number of small files. According to the developers, the new save file format also makes editing audio faster, but on the other side it makes finishing and closing of an audio project a lot slower. It’s important to note that the old .aup save file format can be opened in Audacity 3.0, which will automatically covert it to the new save file format.