How long does it take?

Longer than a desktop app. The encoder is ffmpeg compiled to WebAssembly and runs on one CPU core inside your browser tab, so it is several times slower than HandBrake or a native ffmpeg. In our test on a fast desktop, compressing 1080p video took about four and a half times the length of the clip, so a one-minute clip takes four to five minutes; laptops and phones are slower. The first run also downloads the roughly 32 MB encoder once.

Are my WEBM files uploaded to a server?

No. Your file is read into browser memory, processed on your own device, and released when you close the tab. Nothing is transmitted, stored, or logged at any stage.

Is there a file size limit?

Nothing is capped on our side, but the whole video and the result are held in browser memory. Clips up to a few hundred megabytes work on a desktop; larger files, or phones with little memory, can run out of memory and fail.

Which formats can I use?

MP4, MOV, M4V, WebM and MKV go in. The result is always an MP4 with H.264 video, which plays on practically every phone, browser and editor.

Updated for 2026 • 100% Free Online Video Tool

Free WEBM Video Compressor Online

This video compressor re-encodes your video as an H.264 MP4 using ffmpeg running inside your browser tab, so nothing is uploaded. You choose the quality (CRF) and, optionally, a maximum resolution; audio becomes 128 kbps AAC. In-browser encoding is much slower than a desktop app, so it suits clips of a few minutes. If the result is not smaller than your file, you get your original back.

Your video is processed by ffmpeg running inside this tab, so nothing is uploaded. The first run downloads the ~32 MB encoder once. In-browser encoding is much slower than a desktop app such as HandBrake: expect a 1-minute 1080p clip to take several minutes to compress or resize.

Select or drop your WEBM video

MP4, MOV, WebM and MKV are accepted. The result is always an H.264 MP4.

100% Client-Side Private Processing

Your files are processed locally on your own device. Zero server uploads, zero file storage, and zero tracking.

Zero Server Logs

How WEBM Compression Works Here

Quality slider (CRF 18 to 40, default 28): each step up makes the file smaller and the picture softer. 23 is near-transparent for most footage; 32 and above shows visible smearing in motion.
Resolution cap: limiting a 4K or 1080p phone video to 720p usually saves more than any quality setting, and looks fine on a phone screen.
Never larger: a video that was already encoded efficiently can come out bigger. When that happens you get the original back and the page says so.
Slower than desktop software: encoding runs on one CPU core in WebAssembly. For long or 4K videos, HandBrake on a computer is the better tool.
100% client-side: the video never leaves your device.

Step by step

How to COMPRESS WEBM Files in 3 Steps

1
Select your video
Drop an WEBM, MOV or WebM file into the compressor.
2
Choose quality and size
Leave the quality at 28 for most clips, and add a resolution cap if the video is 1080p or 4K.
3
Compress and save
Wait for the progress bar, compare the sizes shown, then save the MP4.

Common Questions

Frequently Asked Questions

Everything you need to know about the free online WEBM compress tool.

It depends on how the video was recorded. Phone and screen recordings at high bitrates often shrink by half or more at the default setting, and much more with a 720p cap. Videos already compressed for the web may barely change, in which case you get your original back.

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Compress, resize, crop, and convert your files privately — every tool runs inside your browser.

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