How to export a video with a transparent background

Transparent video needs a file format that stores an alpha channel, and Video by Zaweba offers two: ProRes 4444 and WebM with alpha. Build your title, logo or cut-out on a timeline with nothing behind it, open the export window with Ctrl+E, and choose one of those two. The empty parts of the picture stay see-through, so the file can be laid over other footage in any editor that reads alpha.

Most video formats, MP4 included, have no way to say a pixel is see-through. Export an overlay as MP4 and the empty areas turn solid black. So the format matters as much as how you build the graphic.

Which format to choose

ProRes 4444 is the professional choice. It keeps full colour detail and an alpha channel, and is widely read by editing and compositing programs. Files are large, which matters little for short overlays. If someone has asked for "ProRes with alpha", this is what they mean, and 4444 XQ is there when they want the very highest quality.

WebM with alpha suits the web. It is much smaller and can be played by web browsers, which makes it handy for animated overlays on a website. It is less common in editing programs, so check that the receiving program reads it.

Building something transparent

Leave the background empty. Anything on a track below your graphic becomes part of the picture, so mute or remove background footage before exporting. Video by Zaweba can also make transparent video from the Graphics menu, a clip that is see-through from the start, which is a handy base for graphics.

Titles and shapes are naturally transparent around their edges. Add a title with T, draw shapes with the shape tools, or build a layered graphic with Graphics > Graphic with layers, and only the text and shapes will show.

Cut-outs work too. Green screen keying removes a coloured background, masks cut a subject out by shape, and track mattes show a clip only inside the picture on another track. The cut-out parts export as transparent.

Nested sections keep their transparency, so a complex lower third built in a nest still exports cleanly. Animations from Kinetion by Zaweba arrive as transparent WebM through the round trip on the Graphics menu, and can be passed on the same way.

Exporting and testing the overlay

Build the graphic on a timeline with nothing beneath it. Play it through and check the preview: the empty areas should not be filled with a colour.

Set the export range to just the graphic, since each timeline keeps its own export range.

Press Ctrl+E, choose ProRes 4444 (or 4444 XQ) or WebM with alpha, and export.

Test it. Import the file into a fresh timeline over some footage and play it. If the background shows through, the export worked. If it shows black, check that you chose a format with alpha rather than ordinary ProRes 422 or MP4.

Getting a clean edge

Feather masks a little. A hard mask edge looks cut out with scissors; a small feather softens it so the overlay blends with whatever it sits on.

Watch spill on green screen cut-outs. Spill removal takes the green tinge off edges, and it shows far more on a transparent export than in your own composite.

Keep drop shadows and glows modest. Soft effects that fade into transparency come through in ProRes 4444, but very wide ones can look grey over a dark background.

The same idea works inside a project. Clip > Render and replace renders a heavy picture clip to ProRes 4444 with transparency, which keeps a complicated graphic fast to play while still sitting over the footage below it.

Video by Zaweba is free software that works offline, so overlays for clients, channels or websites are made on your own PC with no account.