Ukramedia shows how to use expressions to resize text automatically within a shape, no matter what you type.

Check out this new After Effects expressions tutorial from Ukramedia that shows how you can auto-resize text based on the shape around it. The tutorial shows how to make a little setup where the more you type, the more the text layer will automatically scale when it reaches the bounding edges of the shape.

Sergei Prokhnevskiy and the Ukramedia team often show how to use expressions practically in After Effects.