How to Blur a Background in After Effects

To blur a background in Adobe After Effects, you separate the subject from the background, keep the subject sharp on one layer and apply a blur effect to a copy of the footage underneath it. For moving subjects, the usual way to make that separation is the Roto Brush tool. For a subject that stays put, a hand-drawn mask is enough.

After Effects edits recorded footage after it has been shot. It does not blur your background live during a video call. If you want a blurred background in a meeting, use the blur or virtual background setting in your calling app or camera software. That is a different feature from the editing workflow described here.

Choose the right method

Situation | Method | Why

Subject moves, turns or changes shape (a person talking or gesturing) | Roto Brush plus a blurred duplicate layer | Roto Brush follows the subject from frame to frame, so you do not have to redraw the cutout by hand

Subject stays in roughly the same place (locked-off shot, product on a table) | Mask on a duplicate layer | Faster to set up and quicker to preview than Roto Brush

You already have a depth map or grayscale matte for the shot | Camera Lens Blur with a blur map | Blur strength varies with distance, which gives a more natural depth-of-field look

You want the whole frame soft, with no sharp subject | A blur effect on the single footage layer | No separation needed

Before you start

• Import your footage and create a composition from it. One way is to drag the clip onto the New Composition button at the bottom of the Project panel, which matches the composition settings to the clip.
• Trim the clip to the section you need. Roto Brush analyzes frame by frame, so shorter clips are quicker to process and correct.
• Set the preview resolution in the Composition panel to Full when you check edges. Lower preview resolutions can hide edge problems.

Method 1: Blur the background behind a moving subject with Roto Brush

1. Duplicate the footage layer

Select the footage layer in the Timeline and press Ctrl+D (Windows) or Cmd+D (macOS). Rename the top layer to something like Subject and the bottom layer to Background, so you can tell them apart later. The top layer will hold the cutout of your subject. The bottom layer will be blurred.

2. Isolate the subject with Roto Brush

• Double-click the Subject layer to open it in the Layer panel. Roto Brush only works in the Layer panel, not in the Composition panel.
• Select the Roto Brush tool in the toolbar. Alt+W is the default shortcut.
• On a frame where the subject is clearly visible, paint strokes over the inside of the subject. You do not need to trace the edge exactly. After Effects outlines what it thinks the subject is.
• If the selection includes background areas, hold Alt (Windows) or Option (macOS) and paint over them to subtract.
• To change the brush size, Ctrl-drag (Windows) or Cmd-drag (macOS) in the panel.

3. Propagate the selection and correct it

Step forward through the frames, using Page Down or the timeline in the Layer panel. Roto Brush carries the selection onto each new frame. Wherever the outline drifts onto the background or cuts into the subject, add or subtract strokes on that frame. Fast motion, motion blur, fine hair and backgrounds similar in color to the subject usually need the most corrections.

When the outline holds across the clip, click Freeze in the lower part of the Layer panel. This locks and caches the segmentation, so playback is faster and the selection does not get recalculated.

4. Refine the edges

Applying Roto Brush adds a Roto Brush & Refine Edge effect to the Subject layer, which you can open in the Effect Controls panel. Its matte settings include Feather, Contrast and Shift Edge, which soften, harden or move the edge of the cutout. Use the Refine Edge tool, which shares a slot in the toolbar with Roto Brush, to paint along hair or other fuzzy edges so they keep their detail rather than getting a hard outline. Adjust these by eye. There is no single correct value, because it depends on your footage.

5. Blur the background layer

• Go back to the Composition panel and select the Background layer.
• Choose Effect > Blur & Sharpen > Gaussian Blur for a simple, fast blur, or Effect > Blur & Sharpen > Camera Lens Blur for a softer, lens-like look that takes longer to render.
• Raise Blurriness (Gaussian Blur) or Blur Radius (Camera Lens Blur) until the background looks as soft as you want.
• Turn on Repeat Edge Pixels. Without it, the blur pulls in transparent pixels from outside the frame and leaves dark or soft borders around the edges of the video.

Method 2: Blur the background behind a stationary subject with a mask

• Duplicate the footage layer as in Method 1.
• Select the top layer and draw a mask around the subject with the Pen tool (G) or a shape tool such as the Ellipse tool. With a layer selected, a shape tool draws a mask on that layer.
• Press F with the layer selected to show Mask Feather, then increase it so the edge of the mask blends smoothly instead of looking cut out.
• Apply Gaussian Blur or Camera Lens Blur to the bottom layer, with Repeat Edge Pixels turned on.
• If the subject shifts slightly, keyframe the Mask Path property, or use Track Mask by right-clicking the mask in the Timeline, to make the mask follow it.

Optional: Depth-based blur with Camera Lens Blur

If you have a grayscale depth map for the shot, Camera Lens Blur can use it to vary the blur across the frame. Place the depth map in the composition as a separate layer and hide it by turning off its eye icon. In Camera Lens Blur, choose that layer under Blur Map. Then use Blur Focal Distance to set which depth stays sharp. This produces a more natural falloff than a uniform blur, but it only works if you have a usable depth map. After Effects does not create one from ordinary video in this workflow.

How to tell it worked

• Toggle the blur effect's fx switch on the Background layer on and off. The background should change while the subject stays sharp in both states.
• Scrub through the whole clip, not just the frame you worked on. The subject should stay sharp with no flickering edges, chunks of background attached to it, or missing pieces such as hands or hair.
• Zoom in on the subject's edges at Full resolution. Look for a hard cut-out line, a dark fringe, or a soft halo of the subject smeared into the background.
• Check the outer edges of the frame for dark or soft borders. If you see them, Repeat Edge Pixels is off.
• Play a preview with the Spacebar, or render a short test section. What looks fine on a still frame can flicker during playback.

Those checks confirm the blur and the cutout hold up inside After Effects. They do not tell you how the result will look after export and compression. Render a short test with your final export settings and watch it in the player or platform where it will be viewed.

Common problems and fixes

Problem | Likely cause | What to try

A soft glow or halo of the subject around its outline | The Background layer still contains the subject, and blurring spreads it outward | Use less blur, adjust Shift Edge in the Roto Brush settings, or remove the subject from the background plate (for example with Content-Aware Fill) before blurring it

The cutout edge flickers or shifts during playback | Inconsistent segmentation between frames | Add correction strokes on the affected frames, then adjust the edge settings in Roto Brush & Refine Edge

Hair looks chopped or blocky | Hard segmentation edge | Paint over the hair with the Refine Edge tool

Dark borders around the frame | Blur sampling transparent pixels outside the frame | Turn on Repeat Edge Pixels

Preview is very slow | Roto Brush is recalculating, or Camera Lens Blur is costly to render | Freeze the Roto Brush result, lower preview resolution while working, and switch to Full only for final checks

Limitations to keep in mind

The available evidence does not include tested blur amounts, Roto Brush settings, render times or version-specific feature details, so this guide gives no numeric targets. The right blur strength and edge settings depend on your footage, resolution and the look you want. Start low, raise the values gradually and judge the result on screen at full resolution. Menu locations and tool behavior can also vary between After Effects versions, so if a menu item is not where this guide says, search for the effect name in the Effects & Presets panel.