Grok is a computer software library to encode and decode images in the JPEG 2000 format.

Grok is free and open-source software released under the GNU Affero General Public License (AGPL) version 3.

Grok was forked from OpenJPEG's libopenjp2 in April 2016 by Aaron Boxer under a copyleft license.

As of 2024, the newer, complexity-reduced High-Throughput JPEG 2000 standard (HTJ2K, ISO/IEC 15444-15, ITU-T T.814) has been implemented, with both encoding and decoding support available.

Grok has been integrated into a number of other open source projects, including: This graphics software–related article is a stub.