FL Save RGBA Animated WebP

Animated stickers, logo idents, VFX overlays that need to sit on top of other footage - all of these need a moving image with a transparent background, and that's a genuinely awkward thing to export from ComfyUI. Most animation save nodes flatten your alpha onto black. FL_SaveRGBAAnimatedWebP is built specifically to keep it: give it your color frames and your alpha frames and it writes an animated WebP that's actually transparent, plus a ZIP of the individual PNG frames so you have the raw material too.

The design choice that trips people up first is also the useful one: it takes RGB and alpha as two separate image batches, not one RGBA batch. That's because a lot of ComfyUI workflows carry the matte on a different wire from the color - you generated the subject, you made a mask, and now you want to marry them at export. This node does that marriage. It also builds a preview against a checkerboard background so you can actually see the transparency on the node instead of guessing.

The inputs that matter

• images_rgb (IMAGE) - your color frames.
• images_alpha (IMAGE) - the matte, as an image batch. White = opaque, black = transparent. This is the whole point; if you don't have a real alpha, you don't need this node.
• fps (default 16) - playback speed of the animation.
• lossless (default on) - lossless keeps edges crisp (best for sharp graphics/logos) but makes bigger files. Turn it off to use the quality knob instead.
• quality (0–100, default 80) - only bites when lossless is off; the usual smaller-vs-cleaner tradeoff.
• method (default / fastest / slowest) - encoder effort. slowest squeezes the file smaller at the cost of encode time; fastest for quick previews.

It's an output node, so there are no passthrough outputs - it writes files and shows the preview. You get the animated WebP and a ZIP of per-frame PNGs (with alpha) in your output directory.

Installing it

Ships in ComfyUI_Fill-Nodes. ComfyUI Manager: search Fill-Nodes, install, restart. Or:

cd ComfyUI/custom_nodes
git clone https://github.com/filliptm/ComfyUI_Fill-Nodes

then restart ComfyUI. No model to download - it's an encoder node built on the imaging libraries the pack pulls in.

Where people get burned

The alpha input. If your background isn't cleanly separated, the WebP will show whatever your matte lets through - a grey halo, a hard fringe, a ghost of the original background. The fix is upstream: get a good mask first (a proper background-removal / matting node), and feed that into images_alpha. The checkerboard preview on the node is your early-warning system - if it looks wrong there, it'll look wrong everywhere. Second thing: lossless animated WebP of a long, high-res clip gets large in a hurry. If the file balloons, turn lossless off and drop quality, or switch method to slowest to claw some size back. And remember WebP animation support varies by app - it's great in browsers, patchier in some editors, where you'll want the PNG frames from the ZIP instead.