Free Tool
Compare WebM vs MP4 file sizes — side by side, in your browser
Upload once, encode in three formats, see which is smallest.
The problem
Choosing between MP4 and WebM is usually a guess. "WebM should be smaller" — but by how much for your specific video? Different content compresses very differently. You need to test with your actual file, not trust a spec sheet.
The NSS solution
NSS Video Format Comparison encodes your video into WebM VP9, WebM VP8, and MP4 AVC simultaneously and shows the resulting file size for each. Download whichever format is smallest or best fits your platform.
How to use it
- 1
Choose the right format for your website
Encode your hero or background video in all three formats. Use WebM for browsers that support it and MP4 as fallback — and know the exact size savings before committing.
- 2
Validate compression assumptions
Simple animations and screen recordings often compress better in WebM. Complex film content can be similar across formats. The comparison shows the real numbers for your specific clip.
- 3
Pick the smallest format for mobile delivery
Mobile users pay for data. Compare formats and use the smallest one without quality compromise for your audience.
Step-by-step guide
- 1
Upload your video
Drop or browse to upload. The tool automatically detects which formats your browser supports.
- 2
Wait for all three encodings
Each format encodes sequentially at real time. The progress bar shows which format is currently encoding.
- 3
Compare and download
See file sizes side by side. The smallest is highlighted. Download any format with one click.
Common questions
What quality settings are used for each format?
Browser-default quality is used (no custom bitrate). This matches what you'd get from a basic export. Use the Video Compressor if you need a specific bitrate.
What if a format isn't supported?
If your browser doesn't support a codec, that format shows "Not supported in this browser" and is skipped. Chrome supports all three; Safari has limited WebM VP8 support.
How long does it take?
Each format encodes in real time, so a 1-minute video takes about 3 minutes total (one minute per format).
Ready to try it?
No account. No subscription. No images uploaded to any server.
Compare video formats free→