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WebM to MP4.

Convert WebM to MP4 for the apps that will not take WebM.

→ Open the converterFree, no account, and your video is never uploaded

How it works.

Turn a file that will not open into an MP4 that plays anywhere.

  1. Step 1

    Drag your video in

    Or click to choose a file. It stays on your device.

  2. Step 2

    Read the plan first

    It tells you exactly what will change before anything runs.

  3. Step 3

    Save it as an MP4

    One click, and it downloads.

In detail

WebM is what browsers produce: screen recordings, Loom-style captures, canvas exports, anything a web app rendered for you. It is a fine format that half the world refuses, including most video editors, Premiere, and iMessage. The VP8 or VP9 video becomes H.264 and the Opus audio becomes AAC, in an MP4 that those tools will open.

What it gives you.

  • Plays everywhere by default

    H.264 video and AAC audio in an MP4. Not the newest codecs, the ones that actually open on the machine you are sending to.

  • Streams copied when they already fit

    H.264, AAC, and MP3 tracks are moved across untouched. Copying is lossless and takes seconds, so nothing is re-encoded for the sake of it.

  • iPhone HEVC handled

    Your phone records HEVC inside a .mov because it halves the file size. Windows and older Androids cannot decode it, so that track gets re-encoded to H.264.

  • The containers browsers cannot read

    AVI and other oddities are read by a WebAssembly build of ffmpeg that loads on demand. It is a large one-time download and the tool says so before it starts.

  • Runs in your browser

    Decode, encode, and mux all happen on your machine. The file never leaves it, so there is no upload wait and no queue.

  • No watermark

    Free tool, clean output. The MP4 is your footage and nothing else.

Straight answers.

Why does my screen recording not import into my editor?

Because it is a WebM carrying VP8 or VP9 video and Opus audio, and most editing software only reliably imports H.264 in an MP4 or MOV. The picture is re-encoded here, so expect a wait proportional to the length of the recording rather than an instant copy.

Why will my .mov not play on Windows?

Because of the codec inside it, not the .mov wrapper. iPhones record HEVC (also called H.265), and Windows only decodes HEVC if someone installed the paid extension from the Microsoft Store. Re-encoding that track to H.264 fixes it permanently, which is what this tool does by default.

What is the difference between HEVC and H.264?

HEVC is the newer codec and makes files about half the size at the same quality, which is why phones use it. H.264 is the older one and is decoded in hardware by essentially every device made since about 2010. If a file needs to open on someone else's machine, H.264 is the safe answer.

Does converting lose quality?

Only when a stream has to be re-encoded, and then only slightly at the default setting. Anything already H.264, AAC, or MP3 is copied across byte for byte, which is mathematically lossless. The plan line tells you which of the two is happening before you commit.

My MKV has AC3 surround audio. What happens to it?

AC3 is re-encoded to stereo AAC, because AC3 in an MP4 plays on desktop players and almost nothing else. If you know your player handles it, the advanced options will keep the original audio instead. Only the first audio track is kept either way.

Can it really open AVI files?

Yes. Browsers have no AVI parser at all, so those files go through the ffmpeg fallback, which reads them and always re-encodes the video (AVI-era codecs like DivX and MPEG-4 part 2 have no place in an MP4). It is slower than a copy, and the tool tells you that up front.

Is there a file size limit?

Files that the browser can read natively are limited only by your machine. Files that need the ffmpeg fallback are capped at 1.5 GB, because that decoder is a 32-bit WebAssembly program and cannot address more than that alongside its own buffers. For anything larger, trim it first.

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