Browser & MediaRecorder Compatibility Matrix
This is not a certification: conversion depends on your browser, device, and the file. The converter accepts WebM with one Opus or Vorbis audio track, mono or stereo, up to 45 minutes, and has no fixed conversion speed.
Browser Notes (Not Certified)
| Browser | Operating System | Status | Engine Notes |
|---|---|---|---|
| Google Chrome / Chromium | Desktop (macOS, Windows, Linux) | Expected to work; not certified | Uses Chromium decodeAudioData for WebM Opus/Vorbis, then main-thread JavaScript MP3 encoding. |
| Apple Safari | macOS, iOS, iPadOS | Version-dependent; not certified | WebM Opus/Vorbis decoding depends on the Safari/WebKit version via decodeAudioData; older versions may reject the file. |
| Mozilla Firefox | Desktop & Android | Expected to work; not certified | Uses Firefox decodeAudioData. A missing container duration is not repaired; the decoded audio length is used instead. |
| Microsoft Edge | Windows, macOS | Expected to work; not certified | Uses the Chromium-based decodeAudioData; results follow the installed Edge version. |
| Brave & Opera | Desktop & Mobile | Chromium-based; not certified | Uses each browser's Chromium-based decodeAudioData; extensions and privacy settings were not tested. |
MediaRecorder Recordings Without a Duration
WebM files recorded through the W3C MediaRecorder API can lack a Segment / Info / Duration value, because the recording is written as a stream. Some media players may then show 00:00 or cannot seek.
What conversion does: A bounded metadata preflight reads the WebM header and notes when the duration is missing. The browser then receives the complete file through decodeAudioData, and the 45-minute limit is checked on the decoded audio. The converter creates a new MP3 and does not rewrite the original WebM or add Xing/seek headers. Before download, it checks complete, consecutive MPEG Layer III frame boundaries. The MP3 length includes encoder delay and padding, and duration display and seeking depend on the player.