What is a .webm file? (WebM)

WebM is an open, royalty-free video format built for the web. It uses efficient VP9 or AV1 video and plays directly in modern browsers, which makes it common for background videos and HTML5 players.

What is a .webm file used for?

WebM is a trimmed-down cousin of Matroska aimed squarely at the web. It pairs VP8, VP9 or AV1 video with Vorbis or Opus audio, all free of licensing fees.

Browsers play WebM natively, so it is a favourite for embedded and background video where you want small files and no plugins.

Outside the browser, support is thinner, so for editing or sharing you may convert a WebM to MP4.

How to open a .webm file

The .webm format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list. For a step-by-step walkthrough, see how to open a .webm file.

Windows

VLC
any browser

macOS

VLC
Chrome, Firefox

Linux

VLC
mpv
any browser

Web

Most modern browsers

How to convert a .webm file

You can convert a .webm file to MP4, GIF, MOV using a conversion tool or the export menu of an app that opens it.

.webm file signature (magic bytes)

Programs recognise a .webm file by the bytes at the start of the file, not by its name. These are the signatures for WebM. For a full breakdown, see the WebM file signature page.

Hex signature	Offset	Note
1A 45 DF A3	0	EBML header (shared with MKV)

See the full magic-numbers reference for every format.

Frequently asked questions