The most universal video format is .avi if you want to play video on an pc an a mac. The problem with AVI files is that they aren’t compressed, they are rather large. If you’re looking to keep your file small than your best bet is probably .mov because anyone can download a free player, and mac’s call play .mov files out of the box. A lot of HD video recorders are now recording in .mov because of how well they can compress and how universal the video format can be.
Universal Video Player
A great video format that’s universal with newer browsers is the .mp4 format. It’s what your iOS devices use and plays well on web browsers. A great tool to make sure you video plays on browsers across the board is to use media elements. It falls back to a flash player if your using an older browser that doesn’t support the code to play video.