Slimvid

Preset · WebM to MP4 · stays on device

Convert WebM to MP4 Online

Chrome and many screen recorders save WebM. iPhones, editors and Discord prefer MP4. VP9 cannot be remuxed into MP4, so this is a transcode: the hardware encoder writes H.264, and Opus audio is mapped to AAC so Apple devices play sound. The file stays on your device.

Turn browser recordings into MP4 for iPhone, editors and chat apps.

Drop videos here, or click to browse

Up to 1GB each · MP4, MOV, WebM or MKV

Choose files

Processed locally in your browser. Nothing is uploaded.

Settings

Add a video and the settings for this tool appear here.

How it works

  1. 1Drop the .webm file.
  2. 2Leave MP4 selected.
  3. 3Convert and download.

Processed locally in your browser. Nothing is uploaded.

Process videos up to 1GB on your device. Nothing is uploaded.

WebM plays in Chrome. Not everywhere else.

A Meet or browser recording is often VP8 or VP9 with Opus audio. That combination fails on a lot of phones.

The conversion is almost always a transcode, not a copy. Quality stays close; it is not bit-identical.

If you need the reverse, use the MP4 to WebM page.

What you get

Input
WebM (VP8, VP9 or AV1)
Output
H.264 + AAC MP4
Typical source
Browser recordings

Up to 1GB in the browser.

Checked 2026-10-10.

Three steps

How to convert WebM to MP4

Convert WebM to MP4 online for free, no upload. Local hardware encoding from VP8, VP9 or AV1 into H.264 and AAC.

  1. 1

    Drop your file

    Drop the .webm file.

  2. 2

    Choose settings

    Leave MP4 selected.

  3. 3

    Download

    Convert and download.

All compress-video pagesVideo upload limits in 2026

Same job, other limits

Related size and platform pages

Convert MP4 to WebM OnlineMake a WebM from an MP4 when a site or HTML5 player asks for one.MP4 to WebMConvert MOV to MP4 OnlineTurn iPhone and camera MOV files into an MP4 that plays in browsers, chat apps and slides.MOV to MP4Convert MKV to MP4 OnlineRemux an MKV into MP4 so phones, editors and chat apps will play it.MKV to MP4Compress Video for DiscordHit the 20MB free-upload cap without guessing a bitrate. Hardware encoding, nothing uploaded.For DiscordCompress Video for EmailLand under the 25MB attachment cap so the clip goes through as a file, not a cloud link.For email

Keep going

Related tools

FAQ

WebM to MP4 FAQ

Why does my WebM have no sound on iPhone?
iPhone does not reliably play Opus inside WebM. AAC inside MP4 fixes the silence.
Is quality lost?
A little. VP9 to H.264 is a transcode. It will not be bit-perfect.
Can I go the other way?
Yes. Use the MP4 to WebM page.

Desktop · Coming soon

Desktop · Coming soon

The desktop app is in development. Join the waitlist for launch updates.

Get early accessCompare web vs desktop
  • No file size limit — 4K, hour-long recordings, anything
  • Batch queues: drop a folder, apply one preset
  • Hardware-accelerated encoding (H.264 / H.265)
  • Works fully offline, same privacy guarantee