Split a layer

In the Timeline panel, you can split a layer at any time, creating two independent layers. Splitting a layer is a time-saving alternative to duplicating and trimming the layer—something you might do when you want to change the stacking-order position of the layer in the middle of the composition.
Note: To make new split layers appear above the original layer in the Timeline panel, select Create Split Layers Above Original Layer (Edit > Preferences > General (Windows) or After Effects > Preferences > General (Mac OS)). Deselect this option to make the layers appear below the original layer.
  1. Select one or more layers.
  2. Move the current-time indicator to the time at which to split the layers.
  3. Choose Edit > Split Layer.

When you split a layer, both resulting layers contain all of the keyframes that were in the original layer in their original positions. Any applied track mattes retain their order, on top of the layer.

After you split a layer, the duration of the original layer ends at the point of the split, and the new layer starts at that point in time.

If no layer is selected when you choose Edit > Split Layer, all layers are split at the current time.

Paul Tuersley provides a script on the AE Enhancers forum for splitting layers at layer markers.

Lloyd Alvarez provides a script on his After Effects Scripts website that automatically detects edits in a footage layer and splits it into a separate layer for each edit (or places a layer marker at each edit).