WebM was built for the web. You can play videos directly in your web browser using HTML5 without flash player. However, if you want to play WebM video offline, you may convert WebM to MP4 or convert WebM to AVI with the help of a free webm converter. Everything has two sides, check out the Pros and Cons of WebM below:

1. 100% free and open to everyone.
2. Play video with higher quality and better performance, even on old PCs.
3. Have implemented on more and more popular sites like YouTube, Wikimedia, 4chan, etc.

1. Less supported web browsers currently, only Mozilla Firefox, Opera, and Google Chrome. Internet Explorer 9 and Safari require the third-party WebM Media Foundation Components.
2. Less media players support WebM video or need to install components or plug-ins.
3. WebM video cannot play on most portable devices.