Bento4 is a C++ class library and tools designed to read and write ISO-MP4 files. This format is defined in international specifications ISO/IEC 14496-12, 14496-14 and 14496-15. The format is a derivative of the Apple Quicktime file format, so Bento4 can be used to read and write most Quicktime files as well. The SDK is designed to be cross-platform. The code is very portable; it can be compiled with any sufficiently modern C++ compiler. The implementation does not rely on any external library. All the code necessary to compile the SDK and tools is included in the standard distribution. The standard distribution contains makefiles for unix-like operating systems, including Linux and Android, project files for Microsoft Visual Studio, and an XCode project for MacOS X and iOS. There is also support for building the library with the SCons build system.