Add a background in After Effects

The short answer

To add a background in After Effects, put a new layer (a solid colour, an image or a video clip) below your subject footage in the Timeline panel. After Effects renders lower layers behind higher ones, so the background only shows where the footage above it is transparent. If your footage has no transparency, you first need to remove its original background. With green or blue screen footage you do this by keying. With ordinary footage you do it by rotoscoping.

No version-specific documentation was supplied for this guide. The menu names below are the long-standing ones in After Effects. Check them against the version you have installed, because labels and tool behaviour can change between releases.

Option 1: A solid colour background

• 1. Open your composition.
• 2. Choose Layer > New > Solid. The usual shortcut is Ctrl+Y on Windows or Cmd+Y on macOS.
• 3. Choose a colour. Use the Make Comp Size button so the solid covers the whole frame, then click OK.
• 4. In the Timeline panel, drag the solid below your subject layer.

The composition background colour (Composition > Composition Settings) is not the same thing as a solid layer. It is shown as transparent when the composition is nested inside another composition or rendered with an alpha channel. If you need a colour that always appears in the output, use a solid layer.

Option 2: An image or video background

• 1. Choose File > Import > File (Ctrl+I or Cmd+I) and select your image or clip.
• 2. Drag it from the Project panel into the Timeline, below your subject layer.
• 3. With the background layer selected, press S to show Scale. Resize it until it fills the frame, or right-click it and use Transform > Fit to Comp.
• 4. For a video background, make sure its duration covers the whole length of the subject footage.

Removing the original background first

A new background layer stays hidden until the footage above it has transparent areas. Which method to use depends on how the footage was shot.

Footage type | Usual method | Where to find it

Shot against an evenly lit green or blue screen | Keying | Effect > Keying > Keylight, then use the Screen Colour eyedropper on the backdrop

Ordinary background, no screen | Rotoscoping | Roto Brush tool in the Layer panel, then refine the edges

Simple shape or static subject | Masking | Pen tool or shape tools drawn on the subject layer

Keying usually gives cleaner edges when the screen is evenly lit and the subject is not wearing a similar colour. Roto Brush works on any footage, but it often needs manual correction around hair, fast motion and fine detail. How well either method works depends on the footage, and no measured comparison was available for this guide.

Checking the result

Click the Toggle Transparency Grid button at the bottom of the Composition panel and hide the background layer. Areas that show the checkerboard are transparent. Turn the background back on and scrub through the timeline to look for fringing, flicker or gaps around the subject's edges.

What this means for recorded speech

Replacing a background in After Effects changes only the picture. Keying, rotoscoping and new background layers work on pixels, so they do not change the audio recorded with the clip. If the webcam footage includes its own microphone track, the audio stays with that layer and is exported as long as audio output is enabled in the render settings. After Effects is not a tool for fixing speech problems such as room echo or background noise. It also cannot replace the background live during a video call. For calls, background replacement is handled by conferencing software or virtual camera tools, and those are outside the scope of this guide.