iformat.io
iformat.io
Log In Sign Up

MP4 to WebM Converter

Convert MP4 to WebM free. H.264 is re-encoded to royalty-free VP9 with Opus audio for HTML5 video. Best on short clips — VP9 encoding is slow.

Drop MP4 files here
or click anywhere in this box to choose files

Max file size 50MB. Sign up for more.

What to expect when converting MP4 to WEBM

Typical file-size change
similar at default quality, but slow to produce
Example

Measured on a 1080p H.264 MP4: 8.93 MB in, 9.73 MB out (+9%), taking 14.2s for 10 seconds of video. Expect roughly 1.5x the clip length in processing time.

Quality: Fully re-encoded from H.264 to VP9 and from AAC to Opus. One generation of loss at a fixed quality target.

Best for: HTML5 video on your own site, platforms that require an open royalty-free format.

Avoid when: you need the file to play outside a browser — most TVs, consoles and editors reject WebM.

Tip: VP9 encoding is genuinely slow: about 0.7x real time at 1080p on our hardware, so a clip much over 6 minutes will hit the processing limit. Convert short clips, or keep the MP4 and serve WebM only as a secondary source.

MP4 to WebM: open-format video for the web

MP4 typically contains H.264 video and AAC audio, while WebM uses VP8/VP9 video and Vorbis/Opus audio. VP9 achieves similar compression efficiency to H.264 but is royalty-free. The conversion fully decodes the H.264 bitstream and re-encodes with VP9 (or VP8), which is computationally expensive — expect encoding times 2-5× longer than the video duration. The audio is transcoded from AAC to Opus (preferred) or Vorbis, both of which are high-quality open codecs.

Convert MP4 to WebM for embedding video on websites that prefer open formats, for platforms that specifically require WebM, or when you need a royalty-free video format. HTML5 video elements commonly specify both MP4 and WebM sources for maximum compatibility — WebM for Firefox/Chrome, MP4 as fallback.

MP4 vs WebM: Side-by-side

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

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

MP4 to WEBM FAQ

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

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

How to convert MP4 to WEBM without losing resolution or quality
WEBM is an open, web-optimised video format. Resolution, frame rate, and aspect ratio are all maintained during conversion. The audio track is preserved without re-encoding where possible. For everyday playback and sharing, the visual difference is minimal to none.

My MP4 video won't play — will converting to WEBM fix it?
Usually, yes. Playback failures are almost always a codec or container issue, not corrupted data. WEBM is best for HTML5 video and web embedding and has near-universal device support, so converting from MP4 to WEBM is the quickest way to get your video playing without installing codec packs.

What is MP4?
MP4 is the universally compatible H.264 container, typically used for playback and sharing on any device. Converting it to WEBM makes the file easier to open, share, or upload where MP4 is not supported.

How do I open MP4 files?
On Windows: Media Player, or any browser. On a Mac: QuickTime, or any browser. The safest video format there is. If an MP4 will not play, the codec inside is usually the problem — H.265/HEVC needs an extension on Windows.

Should I use WebM or MP4 for my website?
MP4 (H.264) has near-universal browser support and is the safer choice. WebM (VP9) produces smaller files at equivalent quality but has slightly less broad support. For maximum optimization, serve both using HTML5 <video> with multiple sources.
Need the reverse conversion?
Convert WEBM back to MP4 with our companion tool.
WEBM to MP4 converter

More converters

Browse all
From MP4
MP4 to MP3 MP4 to GIF MP4 to MOV MP4 to MKV

Video Conversion Guides for MP4 to WebM Converter

Read format, playback, upload, and editing guides related to MP4 to WebM Converter.

Video File Formats Explained — MP4, MKV, AVI, MOV, WebM & More

A complete guide to video file formats. Compare MP4, MKV, AVI, MOV, and WebM by quality, compatibility, and when to convert.

How to Compress a Video for Free Online — MP4, MOV, AVI, WebM

Your video is too big for email, Discord, or that upload form. Here's how to compress it down without turning it into a pixelated mess.

How to Convert and Compress Video for WhatsApp

WhatsApp requires MP4 with H.264 codec and files under 16MB. If your video is in the wrong format or too large, here is how to fix it step by step.

How to Convert iPhone Video to MP4 (MOV and HEVC to MP4)

iPhones record video in MOV with HEVC encoding. Here is how to convert to MP4 for sharing, editing, and uploading — plus how to change your iPhone settings to record MP4 natively.

MKV vs MP4: Which Video Format Should You Use?

MKV and MP4 are the two most popular video containers, but they serve very different purposes. Here is when to use each and how to convert between them.

MOV vs MP4: Which Video Format Is Better?

MOV and MP4 are the two most common video formats, but they are not interchangeable. Here's when to use each one and why MP4 wins for almost everything except Apple-specific editing.

Reviewed by Updated