libdmtx is open source software for reading and writing Data Matrix barcodes on Linux, Unix, OS X, Windows, and mobile devices. At its core libdmtx is a native shared library, allowing C/C++ programs to use its capabilities without extra restrictions or overhead.

The corresponding utility programs, dmtxread and dmtxwrite, provide the official command line interface for libdmtx, and serve as a code reference for programmers wishing to use the libdmtx C API. The core library is distributed under the Simplified BSD license, and all other project software uses the LGPLv2 license.

Data Matrix barcodes are two-dimensional symbols that hold a dense pattern of data with built-in error correction. The Data Matrix symbology (sometimes casually referred as "DataMatrix") was invented and released into the public domain by RVSI Acuity CiMatrix. Wikipedia has a good page on Data Matrix and its characteristics.