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WEBM

WEBM Files

WebM Media File

A .WEBM file is an open, web-focused Matroska-based container for VP8/VP9/AV1 video and Vorbis/Opus audio.

WebM multimedia container

Developer
Google, with the WebM Project and Matroska community
Category
Video
MIME type
video/webm
Format
Container
Magic bytes
1A 45 DF A3
First released
2010
Latest version
WebM Container Guidelines / Matroska EBML-based format
Open standard
Yes

Online .WEBM Text Viewer

Reading file…

What is a .WEBM file?

.webm is the extension associated with WebM, which is a freely usable multimedia container format from Google released in 2010 for video use in HTML5 on the web. The extension refers to an implementation of a profile of the Matroska multimedia container format developed by Google and the WebM Project, in conjunction with the Matroska community. This profile of Matroska uses EBML and includes capabilities specific to browser-based and streaming usage, and not all Matroska features.

A WebM file will generally contain video, sound, subtitles and/or meta information; however, in certain cases, the file may be just sound only. Sound only WebM files usually utilize the .webm extension, especially as audio/webm. Popular video formats are VP8, VP9 and AV1. Popular audio formats are Vorbis and Opus where the latter became very popular among web screencasts/downloads.

The use of .webm extensions is mostly associated with downloading from websites such YouTube, capturing from user browsers using MediaRecorder API, screencast tools, chat clients, animations used for websites and video formats for open projects. There are currently no well known and established media formats which would use the .webm format that have nothing in common with the one specified above. Identification should involve examination of EBML headers, and the specific DocType “webm”.

How to open a .WEBM file

Open a .WEBM file on Windows

  1. 1 Go to the folder with your file in File Explorer. Usually, downloaded files end up in Downloads.
  2. 2 Double-click your .WEBM file if you have an app for .webm files on your computer. In case it does not open, move on to step three.
  3. 3 Right-click your .WEBM file -> select Open with -> Choose another app.
  4. 4 Choose VLC media player in the list (Windows 11: choose Always). For Windows 10 -> put a check on "Always use this app to open .webm files" and click OK.

Still not opening? See common problems and fixes.

Programs for Windows

Open a .WEBM file on macOS

  1. 1 In the Finder app, locate your .WEBM file.
  2. 2 Just double-click your .WEBM file in order to automatically launch the program which is connected with it.
  3. 3 Need another app on your Mac? Control-click the file (or right-click with a mouse). In the pop-up menu select Open With -> VLC media player.
  4. 4 If it isn't in the list, choose Other… and find the application manually.

Still not opening? See common problems and fixes.

Programs for macOS

Open a .WEBM file on Linux

  1. 1 Launch your file manager. Depending on the desktop it may be named Files (GNOME), Dolphin (KDE Plasma), Nemo (Cinnamon) or Thunar (Xfce).
  2. 2 Double-click the file.
  3. 3 Or choose another program by right-clicking the file -> Open With -> VLC media player.
  4. 4 Install VLC media player (if it is not installed on your computer) from the software centre, repository or Flathub.

Still not opening? See common problems and fixes.

Programs for Linux

Open a .WEBM file on Android

  1. 1 Launch Files or another file management app.
  2. 2 In Downloads, find the .WEBM file and open it by tapping.
  3. 3 A list of apps capable of opening the file will be shown. Tap VLC media player and press Always to permanently connect the file type with this app.
  4. 4 No apps able to open this file? Download VLC media player from the Google Play Store.

Still not opening? See common problems and fixes.

Programs for Android

Open a .WEBM file on iPhone / iPad

  1. 1 Use the Files app and go to On My iPhone, iCloud Drive or Downloads.
  2. 2 Tap the .WEBM file you want to open.
  3. 3 If the file can be opened by a built-in iOS app (supported format), it opens automatically.
  4. 4 Touch and hold the file to get the context menu -> choose Share -> select VLC media player from the list of apps.
  5. 5 If there is no such option, download the app first from the App Store and then tap the document again.

Still not opening? See common problems and fixes.

Programs for iPhone / iPad

Open a .WEBM file online

  1. 1 Move to the online viewer at the top of this page.
  2. 2 Drag the file there or select it, and its contents will appear in your browser tab. The file is not uploaded.

Still not opening? See common problems and fixes.

Programs for Online

More details about opening .WEBM files

In Windows, such media file types can be used in Google Chrome, Microsoft Edge, Mozilla Firefox, VLC media player, and mpv, most of which use the native codecs for the file extension in concern without an additional pack for VP8/9 and/or Opus. In case when opening by means of double-click opens the app Movies & TV in Windows which cannot decode the required .webm file, one might right click on such media file, choose Open with… and set VLC player or mpv as the preferred program for opening the media file.

On a Mac operating system, modern version of the native browser of Apple - Safari works well with WebM media files, besides the list includes other popular programs such as Google Chrome, Mozilla Firefox, VLC, mpv, Blender software, and DaVinci Resolve. Whether playing or editing WebM media files is concerned, the file format works fine only because of supported codec inside.

On Linux-based systems' desktop, the playback can be supported by Firefox, Chromium, VLC player, mpv, and GStreamer media library, in many cases with the help of media file browser. On the mobile platforms of Google, such media file can be played using browser Google Chrome, Mozilla Firefox, VLC media player, and numerous gallery applications. For iPad or iPhone users, depending on the version of their OS and codec of the .webm media file, Safari, Chromium and other browser, VLC for Mobile, Files and Quick Look will play WebMs.

When talking about the web environment, the HTML5 playback will use video element with attributes like type="video/webm". If a file does not work, one should make sure the file is whole and uncut and that modernized browser or VLC is installed, and codecs in WebM media file should be verified through FFprobe or other apps like MediaInfo.

Technical details

WebM is a binary-based container which uses Extensible Binary Meta Language, known as EBML - the same used in Matroska container. Usually the EBML sign 1A 45 DF A3 followed by EBML Header starts at offset 0, with DocType specifying a document type 'webm'. Since Matroska and WebM have an identical construction and identical magic bytes at start, reliable file identification requires parsing of all EBML elements and not just the first bytes only.

Container consists of EBML elements such as the EBML header; the segment; info; tracks; clusters; cues; tags. Depending on particular profile and muxer, one also has chapters or attachments in WebM, although when used in the browser WebM uses few elements. Typically in the Info and Tags elements WebM contains metadata, such as: duration; timecode scale; language; track name; title; application used for multiplex; application used for writing; creation date; tags' data.

Coding of video and sound in files in WebM format is performed using the codecs stored inside. Typically historically the priority was in usage of codecs VP8 for videos and Vorbis for sound and more recently VP9, and Opus codecs were added with modern browsers being able to work with files that store AV1 codecs in the WebM format too. Usually in comparison with VP8 at equal quality VP9/AV1 formats produce lower size files and also they require more powerful hardware to process the file.

The standard MIME media types of files are video/webm when it includes video stream; also audio/webm for audio files. When one specifies codecs parameter in HTML such as codecs ="vp9,opus" browser knows which decoder to use.

As always, file size is determined by bitrate; its duration and codec choices. Recording video may require a several MBytes, and usually a file containing videos using codecs such as VP9/opus requires tens, hundred megabytes of file space, and there are no restrictions regarding file size in WebM format.

How to convert .WEBM files

If full compatibility is more critical than open code usage, convert the video from .webm to .mp4 using H.264 coding for video and AAC for sound. Target format should allow playing on any iOS-device, older TV, any presentational application, most social platforms not supporting WebM format. In order to obtain identical results you can use FFmpeg software with appropriate settings: ffmpeg -i input.webm -c:v libx264 -crf 23 -preset medium -c:a aac -b:a 128k output.mp4. Alternatively, you can use HandBrake, the software with a GUI if presets are preferred to command lines: HandBrake reads WebM and usually produces MP4 or MKV using codecs such as H.264, H.265, AV1 and audio codecs of choice.

In order to extract an audio stream and convert it one may use FFmpeg with additional parameters -vn (omits video) and save an output as needed (as .mp3 for general purpose playback, as .ogg/.opus for web purposes or .wav as editable audio file): ffmpeg -i input.webm -vn -c:a pcm_s16le output.wav. For cases, where new audio or video codecs are not needed, but remuxing is desirable for some reason and .mkv as target format acceptable you may use FFmpeg in the following way: ffmpeg -i input.webm -c copy output.mkv. Such action won't produce any generation losses. Conversion between audio/video codec produces generation losses in audio/file formats. Conversion into GIF can't be recommended due to large file size in the output and losses of quality in sound and image.

Convert toToolCommand / note
MP4 / H.264 + AAC FFmpeg ffmpeg -i input.webm -c:v libx264 -crf 23 -preset medium -c:a aac -b:a 128k output.mp4 Best general compatibility target for phones, TVs, editing apps, and sites that reject WebM; re-encoding may reduce quality.
MP4 / stream copy when codecs are compatible FFmpeg ffmpeg -i input.webm -c copy output.mkv WebM streams can be remuxed losslessly into Matroska; MP4 usually requires transcoding unless the contained codecs are MP4-compatible.
MP3 audio FFmpeg ffmpeg -i input.webm -vn -c:a libmp3lame -b:a 192k output.mp3 Extracts/transcodes audio from video or audio-only WebM; Opus/Vorbis metadata may not map perfectly.
WAV audio FFmpeg ffmpeg -i input.webm -vn -c:a pcm_s16le output.wav Creates an uncompressed editing/interchange file that is much larger than the original.
Animated GIF FFmpeg ffmpeg -i input.webm -vf "fps=15,scale=640:-1:flags=lanczos" -loop 0 output.gif Useful for short clips only; GIF loses audio, modern color fidelity, and compression efficiency.
Ogg / Opus audio FFmpeg ffmpeg -i input.webm -vn -c:a libopus -b:a 96k output.ogg Good open audio-only target; re-encodes unless the source audio is already suitable for copying into the target container.
MP4 using a GUI HandBrake Open the .webm, choose an MP4 preset, then encode; convenient for batch conversion without command-line use.

Common problems and fixes

In a Web browser, the message "No video with supported format and MIME type found" usually means that there were any of three issues with the server response and the file itself: wrong Content-Type sent from the server, incompatibility of WebM codec with this particular build of browser, or corruption of the container itself. Make sure that video should be sent as 'video/webm' mime type and just plain 'webm' extension should be used, and try opening with 'ffprobe' console tool in order to find out which codecs were used for audio and video.

Message "'Invalid data found when processing input'" generated by FFmpeg usually indicates either partial transfer and need to redownload, or wrong .webm extension for a different format of the video. In case the file has both audio and video streams present, remux it with FFmpeg or MKVToolNix to recover damaged stream(s) and container format.

In case audio plays but the picture is black, check the supported video codecs by trying to open in VLC or mpv (and updating both browser and GPU drivers) if the issue persists - in such way it's quite probable that there's just incompatibility of the specific WebM codecs combination and needs transcoding to more widespread H.264-AAC MP4 in order to make it playable across a wide variety of players.

Some combination of VP9, AV1, audio codecs, alpha channels could make Apple devices and some versions of Safari to stop the playback on certain files. In such case H.264-AAC MP4 conversion is usual recommendation.

Sometimes, the .webm video downloaded from the streaming service could be actually only one part or piece without proper EBML index, missing cues and audio. In such case, use the original program used for downloading in order to merge audio and video parts into one correct WebM video. Also, slow / not possible seek operation should also prompt to reconstruction of EBML index in FFmpeg.

Incorrect associations in Windows could cause such file to open incorrectly as video editor file, and should be reset back to VLC or other player.

Security considerations

Because WebM is a media container instead of an office document format, therefore it has no provision for macros, embedded executables, and scripting capabilities like the Office or PDF. The prime attack vector lies at parse-time through EBML parser, demuxer, decoder for encoded content in codec (VP8/VP9 & Opus), GPU driver stack. Updating browsers (Google Chrome, Firefox, Microsoft Edge & Safari) and media processing application (VLC & FFmpeg) will be recommended in addition to keeping the OS & graphics-drivers up-to-date. Unusual .webm files should be treated similar way like you treat unknown media files - by running them in patched media players, using mainstream codec packages, and wary about the file whose extension looks similar (.exe) but the same gets changed to (.webm). Meta-data can contain information such as creation timestamp, software used for encoding/muxing, title and language. Though remote file loaded within web browser through URL does not gain file-execution permissions from filesystem level.

History and versions

WebM is a web video format introduced in May 2010 during the Google I/O conference that consists of On2 Technologies' VP8 video codec and a Matroska container. After purchasing On2 Technologies in 2010, Google opened-up VP8 for use in WebM and first released it with Vorbis sound. WebM quickly gained support in browsers Chrome, Firefox, and Opera and then from Microsoft and Apple as well but with new updates of the latter browsers. All through the 2010s, VP9, the new Google codec that is supposed to be an extension to VP8, becomes the common WebM video codec and has a large slice of internet streaming, in particular, from YouTube. The standardized speech/multimedia sound codec Opus that was specified via RFC 6716 by the IETF in 2012 became widely accepted in the list of codecs for WebM. Also, there is a newer WebM's video coding standard AV1 which has been completed by AOM in 2018 and used now in WebM by means of new tools and browsers.

.MKV consists of all of Matroska multimedia containers. MKV works well for different codecs, attachments, chapters, subtitles etc, but it is preferred by some users when compared with .Webm for archiving as browser playback does not have limitations like those from Webm. .MP4 uses ISO Base Media File Format and it contains such video standards as H.264, H.265 and AAC, while it usually ensures highest compatibility for the use in portable devices, TV sets and editing programs. .OGV or .OGG are older Ogg Containers with Theora, Vorbis or Opus formats respectively and in browser video playback the best efficiency will ensure WebM Container. .MOV is QuickTime File Format by Apple and it can be commonly found in such processes as camera work or editing, but it may lack good web capabilities as some editing codec might be used there. .AVI is rather outdated container format without any support in modern meta tags or streaming.

Use .M4V format in iTunes or other Apple products to store videos. Use .WebP format for storing images or animations, even small audioless videos. Do not use .AVIF - this format has intra-only codec (for images) AV1, so use .webm for timed audio+videos.

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