WebM vs ProRes 4444 vs HEVC with Alpha vs GIF
Last updated: · Written by the RenderAlpha team
Facts checked against the sources below on November 9, 2026. File sizes measured on FFmpeg 9.0.2; playback tested in Safari 18.6, Firefox 153 and Chrome 152 on macOS 15.6.1.
Only a few video formats can store transparency, and each works in a different set of apps. Pick by where the file will be used, not by quality alone. We made the same 5 second clip in each format and measured what we could.
Short answer
Website or OBS: transparent WebM. Video editing: ProRes 4444. Safari and iPhone: HEVC with alpha. Chats and stickers: GIF. On our 5 second 720p test clip the sizes were 1.0 MB for WebM, 2.3 MB for HEVC, 2.2 MB for GIF and 96 MB for ProRes 4444. An H.264 MP4 cannot be transparent in any of these cases.
Pick by where the file will be used
Match the format to the destination. The last column links to the guide with the details we tested.
| You are making | Use | Why | Guide |
|---|---|---|---|
| A web page overlay | Transparent WebM, plus HEVC with alpha for Safari | Smallest file with soft edges; Safari needs its own file | WebM guide, Safari guide |
| A stream overlay | Transparent WebM | OBS lists .webm as a supported type; we did not test its alpha behavior | OBS guide |
| A clip for a video editor | ProRes 4444 | Apple documents alpha support for 4444 and 4444 XQ | ProRes guide |
| A chat sticker or reaction | Transparent GIF | Plays almost anywhere, but only on or off transparency | GIF guide |
What we measured on one clip
We took a 5 second, 1280×720, 24 fps clip cut out from our own demo footage and saved it in each format on November 9, 2026, with FFmpeg 9.0.2. The settings are in the table. Sizes depend heavily on settings, so read them as an order of magnitude, not a ranking of the formats.
| Format | Settings | Size | Alpha |
|---|---|---|---|
| ProRes 4444 (.mov) | ffmpeg prores_ks, profile 4444 | 96.4 MB | Yes (pix_fmt yuva444p12le) |
| VP9 WebM | CRF 30 | 1.0 MB | Yes (yuva420p when decoded with libvpx) |
| HEVC with alpha (.mov) | hevc_videotoolbox, alpha_quality 0.75 | 2.3 MB | Yes |
| GIF | 480 px wide, 15 fps | 2.2 MB | On or off only |
| H.264 MP4 | CRF 23 | 0.8 MB | No (pix_fmt yuv420p) |
Which browsers rendered the alpha
We loaded the WebM and the HEVC file in three browsers on macOS 15.6.1 and read back a pixel from the transparent area. The result splits cleanly by browser, which is why serving one file to everyone does not work on the web. The Safari guide has the two-source markup we tested.
| Browser | VP9 WebM with alpha | HEVC with alpha |
|---|---|---|
| Safari 18.6 | Not transparent | Transparent |
| Firefox 153 | Transparent | Not transparent |
| Chrome 152 | Transparent | Transparent when loaded directly |
Edge quality and bit depth
Apple’s support page says ProRes 4444 has a mathematically lossless alpha channel of up to 16 bits and supports up to 12 bits per image channel. A GIF is different: MDN describes GIF transparency as one color index that is entirely transparent, so hair and motion blur get hard edges, and each frame is limited to a 256-entry palette. We did not measure the alpha bit depth of the WebM and HEVC files, so we do not compare them here.
What RenderAlpha exports
RenderAlpha exports transparent WebM, ProRes 4444 (up to 10 seconds), transparent GIF and MP4 on a color or image. It does not export HEVC with alpha; the Safari guide shows how to make one with ffmpeg on a Mac. See specs and limits for every number, and how to export with an alpha channel for the routes.
Frequently asked questions
Which video format is best for a transparent background?
It depends on where it plays. Use a VP9 WebM for browsers other than Safari, HEVC with alpha for Safari, ProRes 4444 for editing, and GIF for chats. Pick by destination, as in the table above.
Can an MP4 be transparent?
An H.264 MP4 cannot. Our test MP4 reports pix_fmt=yuv420p, which has no alpha plane.
Why is ProRes 4444 so much bigger than WebM?
ProRes is an editing codec built for quality. On our test clip it was 96.4 MB against 1.0 MB for the WebM, and Apple’s target rate for ProRes 4444 at 1080p is about 330 Mbps.
Does Chrome play HEVC with alpha?
In our test, Chrome 152 returned a transparent pixel when we loaded the HEVC file directly. We tested one Mac, so check your own devices before relying on it.
Is a transparent GIF as good as a transparent WebM?
No for edges. GIF transparency is on or off, so soft edges look hard. It is fine for stickers and simple loops.
Sources
Primary sources we checked. The date is when we last opened each page.
- Apple: About Apple ProRes: alpha support and bit depth (Retrieved )
- MDN: Web video codec guide: Safari and alpha in VP8 and VP9 (Retrieved )
- MDN: Image file type and format guide: GIF transparency and palette (Retrieved )
- Apple WWDC19 session 506: HEVC Video with Alpha: HEVC alpha in Safari (Retrieved )
- OBS Studio: Media Sources: supported file types (Retrieved )