Open web · universal out

WebM to MP4 WebM in. MP4 out.

WebM is a great open-web container — VP9 and AV1 with Opus audio — but iMessage, iPhone Photos, the desktop NLEs, and most TVs still want H.264 in MP4. Morph runs FFmpeg.wasm in your browser tab. The decoder unwraps WebM, the encoder produces a real H.264 + AAC MP4 with a faststart moov atom, ready to play anywhere. Local file in, local file out. No upload, no quota, no watermark.

Open Morph
Drop a file here
WEBM → MP4
Choose a file
Reads and writes inside this tab. Nothing is sent anywhere.

What it actually does

01
DECODE

VP8, VP9, AV1, Opus, Vorbis — all locally.

FFmpeg.wasm decodes the full WebM family. The .webm you grabbed off a recording tool, off YouTube, off a broadcast app — all parse cleanly.

02
ENCODE

H.264 + AAC + faststart

The MP4 is what every player wants. Faststart means the moov atom is up front for streaming.

03
UNIVERSAL

Plays on iPhone

iMessage and Photos both prefer MP4. WebM does not import.

04
LOCAL

FFmpeg.wasm

The video never leaves your machine.

How it works

  1. Open morph.cool in any modern browser.
  2. Drop the .webm — single file or full folder.
  3. Pick MP4 from the format menu. FFmpeg.wasm runs locally.
  4. The .mp4 saves to your downloads. The original WebM is untouched.
  5. Need more than a converter? The rest of Morph runs on your device too — free, with credits only for AI and server work.
3 videoVP8 + VP9 + AV1
0Upload
∞Batch limit

Why people leave the upload-first WebM converters

WebM files are often screen captures, recorded calls, downloaded streams — content where uploading to a third party is the wrong move. Most WebM-to-MP4 sites still POST the file to a server, watermark beyond a free quota, and cap by file size. Morph runs the convert in your browser.

Frequently asked

Why convert WebM to MP4?

WebM is great for the open web. MP4 is universal — iMessage, iPhone Photos, every desktop NLE, every TV. If you grabbed a WebM from YouTube or downloaded a recording from an open-web tool, MP4 is what you want for everywhere else.

Does the file upload?

No. FFmpeg.wasm decodes the WebM and encodes the MP4 in your browser tab. The video stays local.

VP9 → H.264, what about quality?

Re-encoding always introduces some loss. Morph encodes at high bitrates by default. For visually identical output, choose the lossless preset (CRF 18) — file is larger but artifacts are imperceptible.

Audio handling?

Opus or Vorbis from the WebM is decoded and re-encoded as AAC for the MP4 container — every player supports AAC.

AV1 in WebM?

Supported. FFmpeg.wasm decodes AV1 streams; output is H.264 in MP4 unless you pick the AV1-MP4 preset (smaller file, modern players only).

Mobile?

Yes. Safari and Chrome on iOS/Android both support FFmpeg.wasm.

While you're here Open Morph WMV to MP4 AVI to MP4 MKV to MP4 Morph Pro
Convert WebM → MP4
Convert WebM → MP4
Nothing leaves your device · Free for what you make, credits for what we run