Providing video content on the web that is compatible with every client is a moving target. There are a number of formats available, each with their own abilities and weaknesses. Knowing the target audience is the best place to start.

At the time of this writing, Windows was the dominate user platform on the Internet. This means the native video format for Windows machines is a natural choice for being compatible with the largest population of users. The problem is that the default Microsoft AVI format is not very efficient for storing a lot of information in a little space.

The Reference Video.

This is our reference video where everything else in this document started. Note the size and how long it takes from when you click on the file name to when you can view the video.

The GIF Image.

The most common and most widely supported single file video format on the web is the GIF image - yes video file. The format of this graphic file allows multiple images to be stored in the same file and overlaid one on another with an optional timer between each image or frame. This is not very efficient, but is compatible with every graphics-enabled web browser currently available.

This image was created with the freeware Microsoft GIF Animator. Some of the GIF image editing tools with animation ability allow importing AVI movies directly into the GIF format. Since the GIF format was designed for images only, no sound is possible. Our source video did not include an audio track so we have not lost anything. Again, note the file size and the delay between the time when you click on the file name and the time when you start to see the video.

Apple Quicktime.

The folks at Apple have done an amazing job of expanding the scope of the Macintosh QuickTime MOVIE (MOV) video format outside the Mac platform with free viewers for Windows and most UNIX/Linux platforms. Some of the free viewers have a nag screen to remind the user about enhanced pay versions. For most practical uses, the enhanced version gives the user two benefits; removes the nag screen and allows exporting files to different formats. The registered version of the QuickTime 3 player was used to change the AVI file above into the MOV file available here. Note the file size.

Streaming Video.

If you have been viewing the video files as we go, you may have noticed that there can be a very long pause between your clicking on the link and being able to view the video. This is where the file downloads from the web server to your computer. The folks at Real Networks thought this could be improved by allowing the viewer to play the parts as they download. It is called streaming media. This brings some nice benefits to the user such as not requiring a lot of available storage space to download the video before it could be viewed. It also lets those with slower connections to the Internet see what they were receiving sooner and decide if it was not interesting before the full download was complete.

There is one small problem. HTTP is designed for web browsers to get files from web servers in single action connections. There is no easy way to jump in to the middle of a file download to check for streaming media content once the download has started. The way around this is to create a very small file for the web browser to download that is sent to an external player. Once the small file is on the user's computer, it can be passed to a viewer. If that small file contains information on where the real streaming file is located, we get an illusion of clicking on a link and a viewer picking up the connection. This is demonstrated in the following file which contains only one line of text.

The RAM file extension tells the web browser to load the Real Player (or a compatible media player) to read the contents (an address of a video file on this server) and starts playing the video. You can test the difference in how this works by clicking one of the following links at a time and noting the difference in how things work. Remember that the file sizes have been kept small for this demonstration. Imagine how long it would take if the video was several Gigabytes larger.

MPEG Video.

The streaming video is nice, and if you pay for the RealPlayer Plus version there is an option to save some of the video content you download for later viewing. The ability to save content can be disabled by the content provider based on their copyright policy.

There are some people with very slow connections to the Internet that want to trade the low quality of streaming media for the time it takes to download a high quality video file. The AVI format can work for this function, but it is normally large for the quality available and the default encoder does not scale well to full screen. The MPEG (MPG) format offers solutions to both of these concerns. The encoding method used in MPEG files is based on a mathematical formula that allows a viewer to extend beyond the recorded data and better estimate a larger picture than the original. There is no magic here. Eventually the formula will exceed the ability to estimate and the quality will degrade. But this format generally scales up to full screen with better quality than the formats above. Try stretching the size of this video on your machine and go back to the other video formats above and stretch them. Do you see a difference?

All of the discussion above was focused on video formats for the web. One part of the picture that was not covered was how the web server informs the web browser of the content type. For example, have you noticed that some of the web pages you visit have file names with .HTML or .HTM extensions and some have .PHP, .ASP or .CF extensions? They all display as HTML in your web browser. How does this happen? Check out our MIME Type page for IPAD-OS web servers.

First published 2006-12-31. The last major review or update of this information was on 2011-04-07. Your feedback using the form below helps us correct errors and omissions on this page.