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Asset Compressor

Convert MP4 to WebM

WebM with VP9 or AV1 is built for the web: smaller files at the same visual quality, supported by every modern browser. Convert your MP4s locally.

  • No upload
  • No watermark
  • No file size limit
  • Hardware accelerated

Drop videos here to convert them

MP4, MOV, WebM, MKV, AVI and more · no size limit or watermark

Processed on your device. Your videos are never uploaded.

Output format

WebM (VP9/AV1 + Opus) is ideal for websites. Some Apple apps can’t open it – use MP4 for sharing.

Compression

Balanced usually cuts phone videos by 60–80% with no visible difference on a phone or laptop screen.

Resolution
Exact size & social formats

Applies to the shorter side, so 720p works for landscape and vertical videos. Smaller videos are never enlarged.

Advanced: codec, frame rate, audio, trim
Video codec

Auto picks the most compatible codec your browser can encode. H.265 and AV1 are smaller but play on fewer devices.

Frame rate
Audio
Trim

Use m:ss or seconds. Applies to every video in the list.

How to convert MP4 to WebM

  1. 1

    Add your MP4 videos

    Drop in one or more MP4 files – hero videos, product clips or background loops.

  2. 2

    Choose quality

    Balanced is a great default for websites. Background videos without sound can use Small and have the audio removed under Advanced.

  3. 3

    Pick a codec (optional)

    Auto uses VP9. Choose AV1 under Advanced for even smaller files if your browser can encode it.

  4. 4

    Convert and download

    Download the WebM files and upload them to your site.

Why WebM for websites?

Video is often the heaviest thing on a web page. VP9 needs roughly a third less data than H.264 for the same quality, and AV1 even less, so pages load faster and use less of your visitors’ data – good for Core Web Vitals and bounce rates.

VP9 or AV1?

VP9 is supported by practically every browser in use today and encodes quickly. AV1 is the newest royalty-free codec and gives the smallest files, but encoding is slower and not every device can encode or decode it in hardware. Asset Compressor only offers codecs your browser can actually encode.

Serve WebM with an MP4 fallback

For the widest reach, list the WebM file first and the MP4 second in your HTML video element. Browsers pick the first format they support, so modern browsers get the smaller WebM and everything else falls back to MP4.

Tips for background and hero videos

Keep background loops short (5–15 seconds), remove the audio and use 720p or 1080p. Viewers can’t see more detail in a moving background than that, and every megabyte saved makes your page start faster, especially on mobile data.

Frequently asked questions

Is WebM smaller than MP4?

At the same visual quality, WebM with VP9 or AV1 is usually 30–50% smaller than MP4 with H.264. The exact saving depends on the content.

Do all browsers play WebM?

All current versions of Chrome, Edge, Firefox and Opera play WebM, and so does recent Safari. For very old devices, keep an MP4 fallback.

Can WebM videos autoplay as background videos?

Yes, as long as they are muted. Remove the audio track under Advanced to make the file even smaller.

Is anything uploaded?

No. The conversion runs in your browser tab.

How long does converting to WebM take?

VP9 encoding is hardware-accelerated on many devices and usually faster than real time. AV1 takes longer, so try VP9 first if you are converting many videos.

Related tools

WebM to MP4

WebM files from screen recorders and browsers often won’t open in editors, on iPhones or in PowerPoint. Convert them to universally compatible MP4 in your browser.

Compress video

Shrink MP4, MOV, WebM and MKV files on your own device with hardware-accelerated encoding. Choose a quality level or an exact target size – no upload, no watermark.

Video converter

Change a video’s format in seconds. When the codecs allow it, the streams are copied without re-encoding, so the quality stays exactly the same.

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