How do you adjust only one side of a Bezier handle in After Effects?

Adjusting only one side of a Bezier handle in After Effects is accomplished by holding down the Alt key (or Option key on macOS) while dragging the handle. This action allows you to manipulate the handle independently from the other side. By doing so, you can create more nuanced and controlled adjustments to the curve, which is essential for fine-tuning the motion or shape transitions in your animations.

The reason for using the Alt key is that it separates the two handles of the Bezier point, allowing you to create an asymmetrical curve. This capability is vital for animators who need to achieve specific speeds and directions within their motion paths without affecting the entire curve's symmetry.

Using the Shift, Ctrl, or Spacebar keys would not provide the same functionality when adjusting Bezier handles. The Shift key generally constrains movement to angles or specific increment adjustments, Ctrl (or Command on Mac) often allows for duplicating or accessing contextual options, and the Spacebar typically enables panning around the canvas. None of these keys offer the control necessary to independently adjust the handles of a Bezier point as Alt does.