The XviD Codec is a free codec for personal computers that encodes MPEG-4 videos in a compressed format. It takes information in the video file that is not necessary for optimal viewing and strips it out, leaving a file-size that is much smaller, in many cases as small as 1/200th of the uncompressed video. Because of this 200:1 compression ratio and the fact that the XviD Codec is free of charge and open-source (and therefore developer-friendly), XviD is widely used in a number of devices and computer software.

Any video encoded using the XviD Codec will require that the XviD Codec is used to decompress the video for playback or for streaming. Many video player devices support XviD at the hardware level; however, it may be necessary to contact the manufacturer of your video device to determine whether or not XviD is supported. If your PC does not already have the XviD Codec installed, you will need to download and install it in order to play or stream an XviD-encoded video. Fortunately, XviD is free, open-source software, so it's easy to download and install it at no charge.

Once you've downloaded and installed the XviD Codec for your machine, you will be able to play any MPEG-4 video which was compressed using XviD. To find out if a video was compressed with XviD, you can usually look at the filename extension. If the filename ends with ".xvid," then you are probably dealing with an XviD file. Some video files are saved without an extension, or with an extension that does not reflect the file type. In this case, you may be able to determine the video type by looking at the file properties option. If it is an MPEG-4 file, it may be using the XviD Codec.