"Codec" is short for "coder/decoder", and refers to a program or a program plugin that can encode or decode data. When working with video formats, your codecs read your file's encoding and translate it for your media player so that it plays clean video and audio; codecs also translate the file compression, both when first saving your file and when playing it. When saving your 2D or 3D animations into video format, don't forget to check your video compression settings (usually an option under your program settings) and remember that not everyone has the same codec sets as you do.
Consider Common Use in Conjunction With Video Quality.
When selecting a codec when first saving your video file, be aware that while some may have better compression and image quality, they may not be the standard of the common user/web user, so selecting that codec may make it difficult for others to view your content. Try to choose something common--like Microsoft Video 1 or Cinepak--that often comes pre-installed with most operating systems' media players.
Be Aware of Your File Extensions.
Also, don't forget to keep an eye on your file types. .AVI (Windows Media) and .MOV (Quicktime/Apple) are the most common file type formats, but even those can trip you up if you use different compression settings from the commonly accepted standard; AVI files with DiVX compression have been the trend lately, but often require a special player to view unless your Windows Media Player has DiVx support. Alternately, MPEG format is fairly popular, but has such a wide diversity of subsettings (MPEG-4, MPEG-5, etc.) that it can trip up viewers of your media content. The same with the ever-more-popular WMV (Windows Media Video) format
Test Your Final Results.
It may work fine in Premiere or your editing program of choice, but that doesn't mean that your video works elsewhere. Try checking it out in your browser, or in different media playing software (like Windows Media Player vs. WinAmp). If it passes those tests, then send it to a friend or two, or find another way to test it on different machines. This, in the end, will give you the best idea of just how compatible your video file is with other systems, and whether or not it's optimized for the web.
