How to Animate Mask Paths in After Effects

Animating mask paths in Adobe After Effects allows you to morph shapes, reveal content dynamically, and track moving objects with precision. This process relies on keyframing the Mask Path property, which records changes to the mask’s vertices and position across your timeline. This guide covers how to set up an initial mask, generate path keyframes over time, adjust individual anchor points, and refine the resulting motion for smooth playback.

1. Create a Mask

Select the layer in your timeline that you want to mask. Choose either the Pen Tool (shortcut G) to draw a custom shape or one of the parametric shape tools (Rectangle, Ellipse, etc., shortcut Q). Draw your mask directly on the layer in the Composition panel.

2. Enable Mask Path Keyframing

With the layer selected in the timeline, press M on your keyboard to reveal the Mask Path property. Alternatively, twirl down the layer options to locate Masks > Mask 1 > Mask Path. Click the stopwatch icon next to Mask Path to create your first keyframe at the current position of the playhead.

3. Animate the Path Across Time

Move the timeline playhead forward to the point where the transformation should occur. Use the Selection Tool (shortcut V) to modify the mask:

  • Move Entire Mask: Double-click on any vertex to enter transform mode, then click and drag the bounding box.
  • Move Individual Vertices: Click outside the mask to deselect it, then click directly on a single anchor point to select and move it.
  • Add or Remove Vertices: Switch to the Pen Tool to add points to the path or hold Alt (Windows) / Option (Mac) over a vertex to convert it between curved and linear points.

Once a change is made, After Effects automatically generates a new keyframe at the playhead position.

4. Adjust Mask Interpolation

By default, the path will transform linearly between keyframes. To achieve more natural movement:

  1. Select the keyframes on the timeline.
  2. Press F9 (or right-click the keyframe and select Keyframe Assistant > Easy Ease) to smooth the acceleration and deceleration.
  3. Open the Graph Editor to visually adjust the speed and influence handles of the path transition.

5. Fine-Tune Mask Settings

To blend the transformation seamlessly, adjust the supplementary mask properties under the Mask dropdown:

  • Mask Feather: Softens the edges of the mask to prevent sharp cutoffs.
  • Mask Expansion: Dynamically inflates or deflates the mask boundary without altering the underlying path vertices.