libdmtx is a software library that enables programs to read and write Data Matrix barcodes of the modern ECC200 variety. The library runs natively on several platforms and can be accessed by multiple languages using the libdmtx language wrappers. The utility programs dmtxread and dmtxwrite also provide a command line interface for libdmtx, and serve as a good reference for developers writing their own libdmtx-enabled programs.