WEBM to MP4 Converter

WebM to MP4 — fixing the file that nothing will play

WebM files show up most often in one of three situations: you downloaded a video using a YouTube downloader, you exported something from OBS, or you saved a web animation from Reddit or Discord. In all three cases, the same problem shows up — the file won't play on your iPhone, won't upload to Instagram, and won't import cleanly into most video editors.

The fix is converting to MP4. Not because MP4 is technically better, but because every device, every platform, and every piece of software understands H.264 MP4. WebM is a perfectly good format for web use, but outside a browser it's still an orphan.

What the conversion actually does

WebM containers hold VP8 or VP9 video plus Vorbis or Opus audio. None of these codecs live natively inside MP4. So the conversion is a full transcode: each video frame gets decoded from VP9 back to raw pixels, then re-encoded as H.264. The audio gets decoded from Opus and re-encoded as AAC. One generation of quality loss occurs in each stream.

In practice, at standard quality settings you won't see or hear it. The output will look and sound identical to the original for any content you'd normally share or watch.

The file will be bigger — that's normal

VP9 is a more efficient codec than H.264, meaning VP9 achieves the same visual quality at lower bitrates. When you convert to H.264 MP4 at equivalent quality, the output file will be 30–50% larger than the WebM source. That's the cost of wider compatibility. The visual quality is the same; the container is just less efficient at storing it.

Device compatibility before and after conversion

• iPhone and iPad — Safari and Photos app don't support VP9 WebM on iOS older than 15. After conversion to MP4, plays on every iPhone ever made.
• Android phones — VP9 hardware support varies by chipset. H.264 MP4 works everywhere without exception.
• Smart TVs — most Smart TV platforms have no WebM support at all. MP4 is universally supported.
• Social media — Instagram, TikTok, Twitter/X, Facebook, and LinkedIn all require MP4 for video uploads. WebM will be rejected at upload.
• Video editors — Premiere Pro, DaVinci Resolve, and Final Cut Pro import MP4 reliably. WebM support ranges from partial to non-existent depending on the version.

Where WebM files come from

You probably didn't create this file yourself. Common sources: any Chrome-based screen recorder (including Loom on its default settings), YouTube download tools that grab the VP9 stream, Reddit video downloads, Discord video clips, and OBS if it was configured to record in VP9 WebM. If you're seeing WebM files regularly, check whether your tools can be configured to output MP4 directly.