Why convert MP4 to WebM instead of just using the MP4?

WebM is purpose-built for the web. Its modern codec usually produces a noticeably smaller file than the same MP4 at comparable quality, and being open and royalty-free it slots cleanly into a page's video tag. For autoplay backgrounds, hero clips, and embedded demos, a WebM means a faster-loading page.

Will the converted WebM keep its sound?

Yes. WebM carries a full audio track, and LightBox keeps it by default. If you're making a silent autoplay background — the kind browsers require to be muted — switch audio off before converting to trim more size off the file.

Is a WebM smaller than the original MP4?

Usually, and often by a wide margin at similar visible quality, because WebM uses a more efficient codec than the H.264 most MP4s ship with. Exact savings depend on the footage and your settings; lowering the quality, dropping the frame rate, or resizing the width all make it smaller still.

Do all browsers play WebM?

Every current major browser — Chrome, Firefox, Edge, and Safari — plays WebM directly in the HTML5 video element with no plugin. If you need to support very old browsers, a common approach is to offer the WebM first and a fallback alongside it.

Should I choose WebM or animated WebP?

Pick WebM when you want real video: sound, longer runtime, and full playback. Choose animated WebP when you just need a short, silent, GIF-style loop that's smaller and sharper than a GIF. LightBox produces both from the same MP4, so you can try either.

Free online converter

MP4 to WebM Converter

Drop media, a ZIP, or PNG frames

.mp4.mov.webm.gif.jpg.png.webp.heic.zip

Files up to 100 MB free · up to 1 GB with Pro

PNG sequence · Pro

WebM is the web's native video format: open, royalty-free, and built to stream inline in every modern browser. Converting an MP4 to WebM hands you a file that's typically far smaller at the same visible quality — which means quicker page loads and lighter bandwidth for autoplay backgrounds, hero clips, and embedded demos.

Unlike a silent looping image, WebM carries full motion and sound, so it's the right pick when you need actual video — a product walkthrough, a tutorial, a looping hero — not a short muted loop. Keep the audio or drop it, trim to the moment that matters, crop off the bars, and resize to the exact width your layout calls for.

Drop in your MP4 and LightBox does the rest server-side with FFmpeg. Nothing to install, no account to open, and no watermark — your WebM downloads in seconds, and the files are cleared from the server automatically a little while after.

Built for fast-loading pages

WebM's modern codec compresses a bulky MP4 down hard while keeping the picture clean, so background videos and hero sections start playing sooner and eat far less bandwidth. Nudge the quality slider to trade a little detail for an even leaner file.

Your audio comes along

WebM keeps a real audio track, so voiceover, music, or dialogue survives the conversion intact. Want a muted autoplay background instead? Flip audio off and shed even more weight — the choice is one toggle, not a separate tool.

Open format, native playback

WebM plays directly in the HTML5 video tag across current Chrome, Firefox, Edge, and Safari — no plugin, no proprietary licensing, no watermark. It drops straight into a site or app the way the web expects video to work.

Free forever. Pro when you need more.

Everything on this page stays free. Pro adds this — once, no subscription, ever:

1 GB uploads, no daily limit
Batch convert + saved presets
Permanent library, priority processing

$54$2750% off

Launch price · once · yours for life14-day money-back guaranteeSee everything Pro adds

Frequently asked questions

More conversions

Video to WebM Video to Animated WebP PNG to WebP JPG to WebP Compress Video for Web