.GP4 File Extension

Guitar tabs format used by Guitar Pro 4, a multitrack guitar composition and accompaniment program; may contain guitar, bass, or banjo tabs; saves data in a music notation format that can be opened by Guitar Pro or other open-source guitar notation programs.

Fax file saved by various fax programs; contains a generic fax document saved in the CCITT (International Telegraph and Telephone Consultative Committee) standardized Group 4 format, which stores a a 1-bit, or bi-level, image using a lossless compression.

The Group 4 encoding format, designed for data networks, replaced the older Group 3 encoding format. It compresses data into much smaller sizes.