libnbt++ is a free C++ library for Minecraft's file format Named Binary Tag (NBT). It can read and write compressed and uncompressed NBT files and provides a code interface for working with NBT data.
libnbt++2 is a remake of the old libnbt++ library with the goal of making it more easily usable and fixing some problems. The old libnbt++ especially suffered from a very convoluted syntax and boilerplate code needed to work with NBT data.