Y4M to WebM converter
A free Y4M to WebM converter for YUV4MPEG2 files. Browser-based pairs here usually run in this tab, with no file upload.
Drop your Y4M files here
or browse your device · paste with Ctrl+V
Accepts .y4m files. You can queue several files; each is processed one after another on your own device.
Your files never leave this device — there is no upload and no server to delete them from.
- 01
Add your Y4M files
Drop them onto the box above or click to browse. They are read straight from disk — nothing is sent anywhere.
- 02
Check the settings
WebM is already selected. Open the gear icon on any row if you want to change quality, dimensions or codec before converting.
- 03
Download your WebM
Press convert and wait for the row to finish. Convert several files and you can take them all as a single ZIP.
Y4M
YUV4MPEG2Completely uncompressed raw frames behind a tiny text header. Used for codec testing and lossless intermediates; the files are enormous.
- Extension
- .y4m
- MIME type
- video/x-yuv4mpeg2
- Compression
- Uncompressed
- Specification
- Open
WebM
WebMGoogle's royalty-free container built for HTML5 video, pairing VP8 or VP9 with Vorbis or Opus. Smaller than H.264 MP4 at matching quality, and supported by every current browser.
- Developed by
- Released
- 2010
- Extension
- .webm
- MIME type
- video/webm
- Compression
- Lossy
- Specification
- Open
- Y4M is lossless and WebM is lossy. This direction discards some information in the encode step. In practice, many files look identical at default settings, but this is a one-way loss. Keep the Y4M source if you might need a perfect copy later.
Questions about converting Y4M to WebM
Is this Y4M to WebM converter free?
Yes. Converting Y4M to WebM here is free, with no account, no watermark and no daily quota. The work runs on your own device, so there is no server cost to pass on to you.
Is my Y4M file uploaded anywhere?
For browser-based pairs, your file is read locally and converted by ffmpeg in this tab. No file payload is uploaded; you may still see analytics and engine downloads in network logs.
Is there a file-size limit for Y4M to WebM?
There is no imposed upload cap when it runs in-browser, but each conversion still depends on your device and browser memory. Large videos are the first practical limit, then memory-heavy documents or images.
Does converting Y4M to WebM lose quality?
WebM is a lossy format, so some detail is discarded when it is encoded. At the default quality setting the change is often not visually obvious; keep your original Y4M file if you might need it again.
Can I convert several Y4M files to WebM at once?
Yes. Drop in several files and each gets its own row; they are processed one after another on your device. You can download them one by one or as one ZIP.
Does Y4M to WebM work on a phone, Mac or Chromebook?
Most modern browsers on Windows, macOS, Linux, ChromeOS, Android and iOS work. Very large videos are often more reliable on desktop or a browser with more memory.
Why do some conversions take longer on first run?
The conversion engine has to download first. Small codec bundles are fast, while ffmpeg is commonly 12–30 MB; later conversions of similar type use the cached engine.
I converted a file and the output is blank or unusable. What should I check?
Start over with default settings, then change one option at a time (quality, bitrate, page size, or codec) to isolate what changed behavior. If it keeps failing, retry with a smaller file and confirm the source format matches the pair.
Convert other formats to WebM
21 formats can become WebM here.
Convert Y4M to other formats
A Y4M file can become any of these.
WebM to Y4M
The reverse conversion
MP4 to WebM
MKV to WebM
MOV to WebM
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