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QOI's pitch is refreshing: it's a lossless image format with a specification that fits on a single page and an encoder/decoder that takes about 300 lines of code. Created by Dominic Szablewski in 2021, it went viral in the programming community because it proved that a simple format could compress comparably to PNG while encoding and decoding 3-4x faster.
The format uses a handful of simple operations — run-length encoding, pixel differencing, and a small hash table — to achieve compression ratios within 10-20% of PNG. It won't beat optimised PNG tools like ZopfliPNG, but it crushes them on speed. For game engines, real-time applications, and any context where encoding/decoding speed matters more than file size, QOI is compelling.
Adoption is niche but enthusiastic. Several game engines have adopted QOI for runtime texture loading. The reference implementation is public domain. For general image sharing, PNG remains the better choice (smaller files, universal support). QOI is for developers who care about codec performance and appreciate elegant engineering.