Some web designers favor formats that are open-source as they are free to the community to be viewed, used and even enhanced. But the most common issue with open-source work is that it isn't always widely supported. But with the HTML5 <video> tag's stacking capability, you can include multiple file types to try and obtain your preferred file type while still maintaining your video's compatibility.
All of the file types we will be using are lossy file types. They all have undergone some degree of quality compression as original file quality settings would be far too high for web use. For that matter, sometimes even compressed videos can be a difficult balancing act between file size and quality. This issue will be discussed more on the following page. But first, review the table below. These are the most common video file extensions for the web, and their type attribute values to use in the <source> tag.
| File | Ext | Type | Description |
| MPEG-4 | .mp4 | type="video/mpeg" | MP4s are the most common and well-supported video format on the web. This format is the best bet for browser compatibility across the board. |
| Ogg Theora | .ogg | type="video/ogg" | OGG is an open-source format, but has some compatibility issues with some browsers and a number of mobile devices. Audio and video in this format is sometimes differentiated with the file extensions .oga for audio and .ogv for video. |
| Web Media | .webm | type="video/webm" | The WebM format, like OGG, is open-source. However, WebM suffers from fewer compatibility issues and is considered to be more efficient in terms of file size versus quality. |
