WAL
A WAL file is an archive used to store game files in Sly Cooper and the Thievius Raccoonus and Sly 2: Band of Thieves. They are similar to other archive formats, such as RAR and ZIP, but use a different type of compression.
The contents of a WAL archive vary depending on the game build, but they typically contain level data, graphics, videos, music, and sound effects.
History
The WAL format was created by Sucker Punch Productions, the developers of the Sly Cooper series. To date, they have not released the specifications of the format publicly. However, the format has been reverse engineered by some members of the modding community.
Extracting WAL files
WAL files can be extracted using SlyTools. For some games, in order to extract the WAL file you will also need the accompanying WAC, which serves as the table-of-contents for the compressed WAL content.
Some games in the series, such as the PS3 remasters, have their WAC and WAL files exposed in the game's data. Others, like the PS2 release builds, have the WAL encrypted and hidden in the disc image.