The Quite OK Image Format for Fast, Lossless Compression QOI is fast. It losslessly 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. Reference en-/decoder on Github File Format Specification Benchmark Results on 2879