Perian codec is open-source and you can download Perain here. It enables QuickTime to play many popular video formats that not supported by QuickTime natively, like WebM/VP8, MKV. Perian can be recognized as the Swiss-army knife of QuickTime, or saying as add-in of QuickTime. Tutorial on Using Perian for Quicktime to Play Videos of Various Formats on Mac

Best QuickTime Alternative to Play Any Video on Mac You can adopt a way to re-encode all your video files to H.264 to play them in QuickTime by adopting a professional video converting software. So, you may have some videos need to play in QuickTime, such as AVI format, while others require FLV Player or mPlayer or VideoLan Client. Maybe you also have some old WMV-encoded files you'd like to playback. The problem is that there are still many video files which are encoded in XviD and DivX. QuickTime, for example, only supports limited video formats like MPEG-4 and H.264. If you are using a Mac, you may be frustrated when come across many kinds of semi-compatible video formats like FLV, MKV and AVI that makes enjoying movies a daily challenge.

Free quicktime for mac download