WebM to MP4 Converter

Convert WebM to MP4 free. VP8 and VP9 are re-encoded to H.264 so the video plays on iPhone, Apple TV, smart TVs and editors that reject WebM.

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What to expect when converting WEBM to MP4

Typical file-size change

varies with the source bitrate — can halve or double

Example

Measured on 720p clips: a high-bitrate WebM (VP9 CRF 18) came out 42% smaller (7.64 MB to 4.41 MB), while a heavily compressed one (VP9 CRF 45) more than doubled (1.71 MB to 3.49 MB). Typical web downloads landed 7-15% smaller.

Quality: Re-encoded from VP8/VP9 to H.264 at a fixed quality target, with audio re-encoded to AAC at 192 kbps. One generation of loss, generally invisible on normal footage.

Heads up: MP4 doesn't support transparency, so transparent backgrounds in your WEBM will be flattened (usually to white).

Best for: devices that don't support WebM (older iOS, smart TVs, video editing software).

Avoid when: web embedding — WebM is more efficient and widely supported in browsers.

Tip: The output size is set by our encoder's quality target, not by the size of the file you upload. That is why an already-squeezed WebM gets bigger while a high-bitrate one gets smaller — the MP4 is encoded to a consistent quality either way.

WebM to MP4: maximum device compatibility

WebM's VP8/VP9 codecs have strong browser support but limited device support — many smart TVs, game consoles, and older mobile devices cannot play WebM natively. MP4 with H.264 plays on virtually every device manufactured in the last 15 years. The conversion decodes the VP8/VP9 video and Vorbis/Opus audio, then re-encodes with H.264 video and AAC audio. If the WebM uses VP9, the re-encode to H.264 may increase file size by 10-20% at equivalent quality.

Convert WebM to MP4 when sharing video with people on mobile devices, uploading to social media platforms, sending via email or messaging apps, or playing on smart TVs and media players. MP4 is the universal video format.

WebM vs MP4: Side-by-side

Technical comparison of the two formats — useful for deciding which to use, or for confirming what changes during conversion.

Property	WebM	MP4
Full name	WebM (Google)	MPEG-4 Part 14
Year introduced	2010	2001
Developer / standard body	Google	MPEG
MIME type	video/webm	video/mp4
File extension	.webm	.mp4 / .m4v
Compression	VP8/VP9/AV1 video + Vorbis/Opus audio	H.264 or H.265 codec
Color / data depth	8/10/12-bit	8/10-bit
Max dimensions / size	Codec-dependent	Codec-dependent (up to 8K)
Transparency	Yes	No
Animation	No	No
Standard / specification	Open Web Foundation	ISO/IEC 14496-14
Best for	Web-native video, HTML5 <video> tag	Universal video compatibility — plays on every device

Read the full WebM vs MP4 comparison

WEBM to MP4 FAQ

Quick answers about compatibility, quality, metadata handling, and the most common reasons to convert WEBM files to MP4.

How do I convert WEBM to MP4?

Upload your WEBM video to iFormat and click Convert. It's re-packaged into the MP4 container with the optimal codec while resolution and frame rate are preserved. It's free and needs no account.

What is WEBM?

WEBM is an open, web-optimised video format, typically used for HTML5 video and web embedding. Converting it to MP4 makes the file easier to open, share, or upload where WEBM is not supported.

How do I open WEBM files?

On Windows: Any browser; VLC for desktop playback. On a Mac: Any browser, or VLC — QuickTime does not support WebM. A web-first format. Browsers play it perfectly, but desktop and mobile players often will not, which is why it gets converted for sharing.

Why convert WebM to MP4 when WebM works fine on the web?

WebM is web-native, but it doesn't play well outside the browser. Convert to MP4 when you need to: embed in PowerPoint / Keynote, share via iMessage / WhatsApp, edit in iMovie / Final Cut / Premiere, or upload to platforms that reject WebM.

Will the MP4 be bigger than the WebM?

It depends on how heavily the WebM was compressed, because the MP4 is encoded to a fixed quality target rather than to a target size. In our own 720p tests a high-bitrate WebM came out 42% smaller, typical web downloads came out 7-15% smaller, and a heavily compressed WebM more than doubled. If your WebM is already small, expect the MP4 to be larger.

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