QOI is fast. It losslessy compresses images to a similar size of PNG, while offering 20x-50x faster encoding and 3x-4x faster decoding.
QOI is simple. The reference en-/decoder fits in about 300 lines of C. The file format specification is a single page PDF.
The QOI-Logo (framed version) and the specification pdf are released as public domain under the CC0 License and may be freely used.