Convert ProRes 4444 → WebM — free
The one setting that matters
Every classic Render Queue output module has a Channels setting. It defaults to RGB, and RGB is exactly what it sounds like: color only. The alpha channel — everything you spent the composition building — is thrown away at the last moment, and the render comes back with transparency baked to black.
Set it to RGB + Alpha. The color depth gains a "+" (as in Millions of Colors+): that plus sign is the alpha channel. If your render has a black background, this setting is the first thing to check — and the black background guide covers the rest of the suspects.
Straight or premultiplied?
Next to the Channels setting sits the alpha interpretation: Straight (Unmatted) or Premultiplied (Matted). Straight keeps color and transparency fully separate — semi-transparent edge pixels keep their true color and the alpha decides how much of them shows. Premultiplied has the color already multiplied against (usually) black at the edges.
Neither is wrong, but the export and whatever imports the file must agree. Semi-transparent edges — hair, glass, motion blur — get dark or fringed halos when the two ends mismatch. ProRes 4444 conventionally stores straight alpha; when in doubt, export straight and let the receiving editor interpret it — the import guide shows where each editor sets that.
Three output routes
- ProRes 4444. Add the composition to Adobe Media Encoder's queue and render as QuickTime with Apple ProRes 4444 — the alpha rides along when Channels is set to RGB + Alpha. This is the master format Premiere, Resolve and Final Cut expect.
- PNG sequence. Straight from the classic Render Queue: lossless, every frame a transparent PNG, alpha included with RGB + Alpha set. Bulky but universally readable.
- Alpha WebM. After Effects has no built-in WebM export. Either use the free third-party WebM plugin for Adobe apps (check it supports your version), or render the ProRes 4444 master and run it through the free ProRes → WebM converter on this site.
Verify before you deliver
After Effects' own preview composites over its checkerboard, so a broken alpha looks perfect inside the app. Test the rendered file itself: play it over two contrasting backgrounds, or drop it into the free transparency checker, which measures how much of the file is actually transparent — in the browser, no account needed. The alpha test guide has the full checklist.
Questions people are asking
How do I export with a transparent background in After Effects?+
Set the output module's Channels to RGB + Alpha, then render to a format that carries alpha: QuickTime with Apple ProRes 4444 via Adobe Media Encoder, a PNG sequence, or VP9-alpha WebM via plugin or conversion. RGB-only renders bake transparency to black.
Should I export straight or premultiplied alpha?+
Conventional practice is straight alpha for ProRes 4444 masters — semi-transparent edges stay accurate and the receiving editor interprets the alpha. What matters is that the export and the importer agree; a mismatch shows up as dark halos around edges.
ProRes 4444 or PNG sequence?+
ProRes 4444 for a single video file that drops straight into any editor; PNG sequence when the next tool wants frames — game engines, web animations, frame-by-frame workflows. Both carry full alpha; the PNG sequence is lossless but heavy.
Can After Effects export transparent WebM?+
Not without help — WebM export needs the free third-party WebM plugin for Adobe apps. The plugin-free route: render a ProRes 4444 master with RGB + Alpha, then convert it to VP9-alpha WebM with the free converter on this site.