Method 1: Using the Ellipse Shape Tool

How Do I Add a Circle Mask in After Effects?

Adding a circular mask in After Effects is straightforward. You can create a perfect circle mask using either the Ellipse shape tool or by creating a circular mask directly on a layer.

1. Select the Ellipse Tool: In the After Effects Tools panel, select the Ellipse tool (it looks like a circle).
2. Create the Circle: Click and drag on your layer to create a circle. The size and position of the circle will be determined by your mouse movements. This automatically creates a mask. You'll likely notice that by default, the circle mask is a shape layer, not a mask directly on your footage layer.
3. Apply the Mask: To apply this shape as a mask to your footage, you need to create the shape before selecting your footage layer. In many cases, the initial creation makes a shape layer that needs to be used with another method to make it a mask. Or, make sure the mask tool icon in your tools panel is selected.
4. Adjust (Optional): Fine-tune the circle using the mask path editing tools (like the Bézier tool) to achieve perfect circularity or create irregularly shaped masks. This is especially important if you're trying to create a mask within an existing shape (like a square).

Method 2: Creating a Circular Mask Directly on a Layer

1. Select the Layer: Select the layer to which you want to add the circular mask.
2. Select the Mask Tool: Select the Mask tool from the toolbar (it's usually represented by a square with a circle inside). Important: Make sure you have your footage layer selected before selecting the mask tool.
3. Create the Circular Mask: Hold down the Shift key while you click and drag with the mouse on the layer to create a perfect circle. Releasing the mouse creates the circular mask.

Troubleshooting

• Mask appears as a square: This can happen if the layer's scale, transformation or effects properties interfere with the mask's shape. Check the scale and position of your layer, and ensure there are no conflicting effects distorting it. Adjust accordingly. In some instances, this may require recreating the mask.
• Imperfect circles: Ensure you hold down the Shift key while drawing the circle with the ellipse tool to constrain its proportions to a perfect circle.

This method effectively creates a circular mask in After Effects, allowing you to reveal or hide portions of your layer. Remember to adjust the mask feather and opacity properties for refined control over the masking effect.