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WebM files: what they are and how to convert WebM to MP4

WebM is the open web video container (VP8, VP9, or AV1 video with Opus or Vorbis audio) produced by browser-based screen recorders and Chrome extensions. It works well in browsers, but iPhones, TVs, and most editing software will not open it.

Usual codecs
VP8 or VP9, Vorbis or Opus
Plays on
Browsers, Android; Apple partly
Subtitles
WebVTT
Best for
Web pages, screen recordings

What is a WebM file?

WebM is the open, royalty-free video container Google launched in 2010 for the web. It holds VP8, VP9, or AV1 video with Vorbis or Opus audio. Browsers record to WebM natively, which is why screen recordings from Chrome extensions, Loom-style tools, Discord clips, and many web apps arrive as .webm files.

Where WebM fails

iPhones, iMovie, PowerPoint, most video editors, and many upload forms do not accept it. Unlike MOV, converting WebM to MP4 requires a real re-encode, because MP4 cannot carry VP8 or VP9 video. That takes about real time for 720p footage in the browser and produces an H.264 file that plays anywhere.

Going the other way

Some wikis and open-source projects require WebM for embedded video. MP4 to WebM re-encodes to VP8 with Vorbis audio, which every modern browser plays natively. WebM clips also make good source material for GIFs.

Frequently asked questions

Why is WebM to MP4 slow?

The video must be decoded and re-encoded as H.264, frame by frame, on one CPU core. Short clips take a minute or two.

Does WebM play on iPhone?

Safari on iOS 15 and later plays it in the browser, but the Photos app and iMovie do not. Convert to MP4 to share with iPhone users.

Convert or edit WebM files

WebM to MP4.webm → .mp4Compress VideoShrink MP4, MOV, WebM, and MKV videos for email, Discord, and messaging appsCompress Video for DiscordShrink a video to fit the Discord upload limit (10 MB free, 50 MB Nitro Basic, 500 MB Nitro) in your browserCompress Video for EmailMake a video small enough to attach to an email (25 MB Gmail and Outlook limit, or 20 and 10 MB) in your browserCompress Video to a Target SizeCompress a video to an exact maximum file size (8, 10, 16, 25, 50, 100, or 200 MB) in your browser for WhatsApp, Telegram, forums, and uploads with limitsTrim VideoCut a clip out of an MP4, MOV, WebM, or MKV by start and end time in your browserCrop VideoCrop a video to square, vertical 9:16, 4:5, or 16:9 in your browser, centered, for Reels, TikTok, and ShortsRotate VideoRotate a video by 90, 180, or 270 degrees or mirror it, in your browserMute VideoStrip the audio track from an MP4, MOV, WebM, or MKV in seconds, without re-encoding the videoChange Video SpeedMake a video faster or slower, with the audio pitch preserved, in your browserVideo to FramesSave frames from a video as JPG images at a chosen rate (one per second, five per second, every frame) in your browser, downloadable as a ZIPVideo to TextTranscribe the speech in a video to text on your device with Whisper: MP4, MOV, WebM, MKV in, plain text plus SRT and VTT subtitles outMP4 to MP3.mp4 → .mp3Audio to TextTranscribe MP3, WAV, M4A, OGG, and FLAC recordings to text on your device with WhisperTrim AudioCut a section out of an MP3, WAV, M4A, FLAC, or OGG file by start and end time, in your browserChange Audio VolumeMake an audio file louder or quieter, or normalize it to a standard loudness, in your browserVideo to GIFTurn MP4, MOV, WebM, or MKV video clips into high-quality GIFs in your browser

Make WebM files

MP4 to WebM.mp4 → .webm