Codec Definition Codec is short for "coder-decoder." It is an algorithm used to encode data, such as an audio or video clip. The encoded data must be decoded when played back. A media codec is not equivalent to media compression, since it is possible to encode a file without compressing it. However, most codecs do compress the original data, reducing the size of the original file. This is important for multimedia files, since they often have large file sizes. Compressed files take up les...