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WebM Format: The Open Source Future of Web Video

5 min read

WebM Format: The Open Source Future of Web Video

If you browse the web today, you are constantly consuming video. From massive 4K YouTube uploads to tiny, looping animations in the background of modern landing pages, video is everywhere. For a long time, the MP4 format was the undisputed king of web video.

However, in 2010, Google introduced a new contender designed specifically for the unique demands of the internet: the WebM format.

WebM promised to be open, royalty-free, and highly optimized for web delivery. Today, it is a foundational technology for modern web development. In this guide, we will explore what a WebM file is, how it works, how it compares to MP4, and why you should be using it.

What is a WebM File?

WebM is an audiovisual media file format. Like MP4 or AVI, WebM is a container format. This means the WebM file itself doesn't define the video or audio; it simply holds (containers) the video streams and audio streams together.

The defining characteristic of WebM is what it is allowed to hold inside that container:

  • Video Codecs: WebM exclusively uses the VP8, VP9, or AV1 video codecs.
  • Audio Codecs: WebM exclusively uses the Vorbis or Opus audio codecs.

Because Google tightly controls the specifications of the WebM container, it guarantees that every WebM file is entirely open-source and free of the complex patent licensing that plagues older formats.

The Origins of WebM

To understand why WebM was created, you have to look at the state of web video in the late 2000s.

Before HTML5, embedding a video on a website required clunky, proprietary plugins like Adobe Flash. When the HTML5 <video> tag was introduced, it allowed browsers to play video natively. However, there was a massive fight over which video format should be the standard.

Apple and Microsoft pushed for MP4 (H.264). The problem was that H.264 is a patented technology owned by a consortium called MPEG LA. Using it commercially often required paying licensing fees, which went against the open nature of the web.

In response, Google acquired a company called On2 Technologies, which had developed a highly efficient video codec called VP8. Google immediately open-sourced VP8, paired it with the open-source Vorbis audio codec, packaged them in a container based on the Matroska (MKV) format, and released it to the world as WebM.

WebM vs. MP4: The Heavyweight Bout

Today, the two dominant formats for web video are WebM and MP4. How do they compare?

1. File Size and Quality

  • WebM (using VP9 or AV1): Generally provides better video quality at significantly smaller file sizes compared to standard MP4 (H.264). This makes it vastly superior for web delivery, as it saves server bandwidth and loads faster for users on mobile networks.
  • MP4 (using H.264): Larger file sizes, but highly consistent quality. (Note: MP4s using the newer H.265 codec offer excellent compression, but H.265 is burdened by even heavier licensing fees and poor browser support).

2. Licensing and Patents

  • WebM: 100% open-source and royalty-free. Anyone can develop software to create or play WebM files without paying a dime.
  • MP4: Proprietary and heavily patented. While free for end-users, large platforms and software developers often have to pay licensing fees to MPEG LA.

3. Compatibility

  • MP4: The king of universal compatibility. An MP4 will play on literally any device, browser, smart TV, or operating system made in the last 15 years.
  • WebM: Excellent support on modern web browsers (Chrome, Firefox, Edge, and eventually Safari). However, it lacks native support on many older smartphones, smart TVs, and legacy video editing software (like older versions of Premiere Pro).

Why Web Developers Love WebM

If you are building a website today, WebM offers several killer features that make it the format of choice for modern design.

Alpha Channel (Transparency)

This is arguably WebM's best feature. A WebM video can have a transparent background. You can film a subject on a green screen, remove the background, and export it as a transparent WebM. When placed on a website, the website's background will show through the video. MP4 does not support transparency.

The True GIF Replacement

As discussed in our GIF format guide, animated GIFs are massive, inefficient files that destroy page load times. A looping, silent WebM file can provide vastly superior animation quality at a fraction of the file size of a GIF, dramatically improving your website's performance and Core Web Vitals.

How to Implement WebM on Your Website

Because WebM is not supported by every single legacy device (specifically older iOS devices), web developers use a technique called fallback routing using the HTML5 <video> tag.

You provide the browser with a highly optimized WebM file first. If the browser doesn't know how to play WebM, it automatically falls back to a standard MP4 file.

<video autoplay loop muted playsinline>
  <!-- Modern browsers will play the tiny WebM file -->
  <source src="animation.webm" type="video/webm">
  <!-- Older browsers will fall back to the larger MP4 file -->
  <source src="animation.mp4" type="video/mp4">
  Your browser does not support the video tag.
</video>

Conclusion

WebM is the format built by the web, for the web. By combining open-source ideals with cutting-edge compression technology (VP9 and AV1), WebM has ensured that the future of internet video remains free, fast, and accessible. While MP4 remains necessary as a universal fallback, WebM is the tool you should reach for when performance, transparency, and efficiency are your top priorities.

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