Because there are many video codecs. There seems to be no video file he can't open. The program supports many video formats and installs the necessary plug-ins (codecs) to play videos of this format.

If you want to play different formats, it downloads the necessary plugins from an open source plugin site free of charge and automatically. GOM Player can automatically install decoders such as XviD, DivX, FLV1, AC3, OGG, MP4, H263.