Basics of Masks in After Effects

In this tutorial, you’ll learn the basics of using Masks in Adobe After Effects. Masks let you control which parts of a layer are visible, making them essential for creating reveals, isolating content, or targeting effects to specific areas. We’ll show you how to draw, adjust, and animate masks and combine multiple masks for more complex designs. By the end, you’ll be able to use masks to shape your visuals with precision.

Masks let you control which parts of a layer are visible by drawing directly on the layer itself. Unlike track mattes, masks are built into the layer, giving you hands-on control over shapes, edges, and animation.

What Is a Mask?

A mask is a path that defines a visible or hidden area of a layer. You can draw a mask to crop part of a video, create a custom reveal, or isolate an object. Masks are great for detailed control, especially when you only need to affect one layer.

Masks are vector-based, which means they can be adjusted at any time by moving points and handles.

Creating a Mask

You can create a mask in two main ways:

Shape Tools

1. Select a layer in the timeline.
2. Choose a shape tool (Rectangle, Ellipse, etc.) from the toolbar.
3. Click and drag in the Composition panel.

This creates a mask on that layer using the shape you drew.

Pen Tool

1. Select a layer in the timeline.
2. Select the Pen tool from the toolbar.
3. Click to create points and draw a custom path.
4. Click and drag to create curves.

The Pen tool gives you the most control for detailed or irregular shapes.

Mask Modes

Once you’ve created a mask, After Effects gives you several mask modes in the timeline, including:

• Add: Makes the area inside the mask visible.

• Subtract: Hides the area inside the mask.

• Intersect: Shows only the overlapping area between multiple masks.

• None: Disables the mask without deleting it.

These options are found in the Mask settings dropdown under the layer’s properties. 

Adjusting a Mask

Masks are editable after you draw them:

• Move points: Use the Selection tool to click and drag points or handles.

• Move the whole mask: Click the mask path and drag it.

• Feather: Softens the edges of the mask.

• Expansion: Grows or shrinks the mask shape without changing the points.

• Opacity: Adjusts how transparent the masked area is.

You’ll find these settings by twirling open the mask under your layer in the timeline.

Animating a Mask

You can animate a mask’s shape over time by setting keyframes:

1. Expand the Mask Path property.
2. Click the stopwatch to set a keyframe.
3. Move forward in time and adjust the shape.
4. After Effects will animate the mask between the two shapes.

This is useful for custom reveals, wipes, or isolating a moving subject.

Masks vs. Track Mattes

Use masks when you need precise control on one layer. Use track mattes when you want to reuse visibility control or apply it to multiple layers.

Tips for Using Masks

• Use feathering to avoid hard edges.

• Combine multiple masks for complex shapes.

• Use Subtract masks to cut holes in shapes or footage.

• Press M to quickly show all masks on a layer, or MM to expand all mask settings.

Wrap-Up

Masks are essential for isolating elements, revealing content, and shaping what the audience sees. They give you precise, frame-by-frame control and are flexible enough for both design and cleanup tasks.

In the next lesson, we’ll explore Parenting and Puppet Tools, two features that help you link and animate elements in more advanced ways.