WebM to MP4 converter

To convert WebM to MP4, drop the file here and press Convert to MP4. A WebM holds VP8 or VP9 video and Opus or Vorbis sound, which many editors, phones and apps won't take, so they're re-encoded to H.264 and AAC: the MP4 plays and edits anywhere. Free, and nothing is uploaded.

A free tool from Clyper, the AI clipping tool that turns long videos into captioned vertical clips.

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Converted on your device: nothing is uploaded.

Make HEVC (H.265) videos H.264iPhones record HEVC. Copied into MP4 it plays on phones, Macs and most browsers, but some Windows PCs and editors can't open it. H.264 plays everywhere; it's re-encoded, so it takes about as long as the video plays.

Free, no watermark, nothing to sign up for. Copying has no length limit; up to 60 minutes of a video can be re-encoded at a time.

How to convert WebM to MP4

Drop your WebM files in, or choose them: up to 20 at once. Each shows its length, size and what's inside it.
Press Convert to MP4. The picture becomes H.264 and the sound AAC. It takes about as long as the video plays, so keep the tab open.
Download each MP4, or all of them at once, and post, send or edit it anywhere.

Only need it smaller, not in another format? The video compressor makes an MP4 to a size you pick, from a WebM too.

WebM and MP4 side by side

WebM and MP4 compared
	WebM	MP4
Picture	VP8 or VP9 (AV1 too)	H.264 or HEVC (AV1 too)
Sound	Opus or Vorbis	AAC or MP3
Built on	Matroska, the same base as MKV	Apple's QuickTime format
Made for	Playing in web pages	Everything: phones, editors, TVs, apps
In this converter	Re-encoded to H.264 and AAC	Already there

Where WebM files come from

WebM is the web's own video format, so it turns up wherever video is made inside a browser: screen recorders that run as a web page or an extension, video calls and meetings recorded in the browser, and clips saved from web pages. It plays fine in Chrome and Firefox, which is why it's only a problem once the file leaves the browser for an editor, a phone's gallery or an upload form.

What happens to the sound

WebM sound is Opus or Vorbis. The converter re-encodes it to AAC, the sound in nearly every MP4. In the rare browser that can read Opus but can't make AAC, the sound is made MP3 instead, which MP4 players play too, and the row tells you.

Want just the sound of a recording, for a podcast or notes? Turn it into an MP3 with the video to MP3 converter, or into text with video to text.

Questions

How do I convert WebM to MP4?

Drop the WebM file here and press Convert to MP4. Its VP8 or VP9 picture is re-encoded to H.264 and its Opus or Vorbis sound to AAC, the formats every phone, editor and app takes. Keep the tab open until it's done.

Why does it re-encode instead of copying?

Because the picture and sound in a WebM aren't the kinds MP4 players expect. An MP4 can technically hold VP9 and Opus, but plenty of players and editors won't open it, so the converter makes H.264 and AAC, which play everywhere.

Does it lose quality?

A little, as any re-encode does, but it's encoded at a high bitrate so the difference is hard to see. Screen recordings with sharp text come through well. Copying, with no loss at all, only happens for videos that already hold H.264 or HEVC.

Why is my MP4 bigger than the WebM?

VP9 squeezes the same picture into less space than H.264, and the MP4 is made at a generous bitrate to keep it sharp. If it needs to be smaller, run it through the video compressor afterwards.

How long can the WebM be?

Up to 60 minutes of video re-encoded at a time, and up to 20 files in one go. For a longer recording, split it first with the video splitter. It takes about as long as the video plays, faster on a computer than a phone.

Is the file uploaded?

No. It's read, re-encoded and saved by your browser, on your device. Free, with no watermark and nothing to sign up for.

Sources

Read on November 7, 2026.

Recorded a webinar or a call?

Upload it to Clyper as it is (WebM works) and it finds the moments worth posting, frames each one vertically and captions every word: up to 30 clips, ready for TikTok, Reels and Shorts.

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