How to Make a Background Transparent in After Effects

The short answer

In After Effects, a transparent background is stored in an alpha channel. Any area of a composition with no visible pixels is already transparent, even though the panel shows it in the composition's background color. That color is only a preview and is not rendered. To remove a background that is part of your footage, first isolate the subject. You can key out a solid-colored screen, use Roto Brush on an ordinary background, or draw masks around simple shapes. Then render to a format that supports alpha with the channels set to include it. The main limit is the export. If you render to a format without alpha support, such as typical H.264 delivery files, the transparent areas become solid again.

Check that the background is actually transparent

Turn on the Toggle Transparency Grid button at the bottom of the Composition panel. Transparent areas then show as a checkerboard instead of the background color. This is the quickest way to confirm that a key or roto matte is working before you render.

Choose a removal method

Method | Best suited to | Main limitation

Keying (Keylight) | Subjects filmed against an evenly lit green or blue screen | Uneven lighting, wrinkles and color spill on the subject reduce edge quality

Roto Brush | Subjects against an ordinary room or office background | Needs review and correction across frames, especially around hair and fast motion

Masks (Pen tool) | Static shots or subjects with simple, well-defined shapes | Moving or complex outlines need keyframed mask paths, which is slow

Key out a green or blue screen

• Select the footage layer in the timeline.
• In the Effects & Presets panel, search for Keylight and apply it to the layer.
• Use the Screen Colour eyedropper to sample the background color close to the subject.
• Switch the view to Screen Matte. In that view, white is kept and black becomes transparent.
• Adjust Clip Black and Clip White until the background is solid black and the subject is solid white, without losing fine edges.
• Switch back to Final Result. If needed, add Key Cleaner to restore edge detail or Advanced Spill Suppressor to reduce green or blue fringing on the subject.
• Turn on the transparency grid and scrub through the clip to confirm that the background stays removed.

Remove an ordinary background with Roto Brush

• Double-click the footage layer to open it in the Layer panel.
• Select the Roto Brush tool from the toolbar.
• Paint over the subject on a representative frame. Hold Alt (Windows) or Option (macOS) while painting to subtract areas that were included by mistake.
• Let After Effects propagate the selection through the clip. Step through the frames and correct any frames where the edge drifts.
• Use the edge refinement options for soft details such as hair.
• When the selection holds across the clip, use Freeze to lock it so it does not recalculate.
• Return to the Composition panel and check the result against the transparency grid.

Use masks for simple shapes

Select the layer, pick the Pen tool and click around the area you want to keep to draw a closed path. The area outside the mask becomes transparent. Use mask feather to soften the edge. If the subject moves, keyframe the Mask Path property, or combine a rough mask with a key to remove clutter that the key cannot handle.

Export with the transparency intact

• With the composition active, choose Composition > Add to Render Queue.
• In the Render Queue, open the Output Module settings.
• Choose a format that supports alpha. Common choices are QuickTime with Apple ProRes 4444 or the Animation codec, or a PNG image sequence.
• Set Channels to RGB + Alpha.
• Render, then import the file into a new composition or your editor and confirm that the checkerboard shows through where the background was.

You can also send the composition to Adobe Media Encoder. The same rule applies there: pick a preset and codec that support alpha. Presets aimed at web delivery generally do not.

What this means for recorded speech

Removing a background is a video-only process. Keying, rotoscoping and masking do not change the audio on the layer, so the voice your webcam or microphone captured is unaffected. Audio can be lost at export, though. Image sequences such as PNG carry no audio. A QuickTime render includes audio only if audio output is enabled in the Output Module. If you need an alpha-channel video and the speech together, enable audio output on a QuickTime render, or render the audio as a separate file and recombine the two in your editor. Replacing the background also does nothing to reduce room noise or echo picked up by the microphone. That has to be handled at capture or with audio tools.

Gaps in this guide

Menu names, effect names and Roto Brush behavior differ between After Effects versions, and no version-specific documentation was supplied for this guide. Check the labels in your installed version if a step does not match. This guide also includes no testing, measurements or quality comparisons between the methods.