SF3 (Simple File Format Family) is a family of open standard binary file formats, free to use for everyone. These file formats all follow a similar scheme and the same principles.
Included are formats for images, audio, 3D models, rich text, logging, archives, and more. All of the formats are intended to be easy to read and write, and cover base use-cases of various binary formats. You may want to use one of these formats if you need a simple alternative to common formats that is nonetheless specified and not ad-hoc, or require a format that allows for very fast in-memory access.
You can find more information about the formats at the links below:
You can also find reference implementations for the formats at these links: