How to precompose each layer separately in After Effects

Why does After Effects put all my layers into one precomp?

Because grouping is what Pre-compose is for. Select five layers, choose Layer › Pre-compose (Ctrl+Shift+C, or Cmd+Shift+C on a Mac) and all five go into one new comp, which then sits in your timeline as a single layer. The dialog has no "one per layer" option.

It does give you two choices, and only one of them works with several layers:

Name the precomp in the same dialog, or the Project panel fills with numbered pre-comps that someone has to sort out later.

How do I precompose each layer separately by hand?

One layer at a time. For each layer:

1. Click the layer so it's the only one selected.
2. Press Ctrl+Shift+C (Cmd+Shift+C on a Mac).
3. Type a name. The layer's own name is usually the right one.
4. Pick Leave or Move (see the table above) and press OK.
5. Click the next layer and repeat.

Twenty layers means twenty trips through the dialog. The usual mistake is two layers selected by accident and merged into one precomp. Watch the timeline after each OK: if two layers vanished and one came back, undo.

If you do this often, put the shortcut on a mouse button. mouzeclick's per-app mouse buttons and gestures run any key combination, on Windows and Mac, and only fire while After Effects is in front. It still opens the dialog each time; it just saves the reach.

How do I precompose every selected layer at once?

Select the layers and press Precomp sep in the Toolbox of the mouzeclick workspace for After Effects. Each selected layer gets its own precomp in one press. Alt-click the button and each precomp is also cropped to its content.

1. Install mouzeclick on Windows; it adds the workspace to After Effects.
2. Open Window › Extensions › mouzeclick workspace and switch to Toolbox, one of the quick workspaces at the bottom of the panel.
3. Select the layers in your comp.
4. Click Precomp sep, or Alt-click it to crop each new precomp to its content.

A 300-pixel logo pre-composed the normal way sits in a full 1920×1080 frame, so its precomp layer's box is the size of the whole screen. Cropped, the precomp is about the size of the logo and its box hugs it in your comp. If a layer has a glow or a drop shadow that spills past its edges, check it after a crop, and check that each precomp still sits where you expect.

To crop a precomp by hand, open it, draw a region of interest around the content with the Region of Interest button under the Composition panel, then choose Composition › Crop Comp to Region of Interest. The crop changes where the content sits relative to the comp's centre, so line the precomp layer up again in the parent afterwards. Toolbox also has Comp cut, which crops the open comp to its content.

How do I duplicate a precomp without linking it?

Duplicate the comp in the Project panel and swap the copy in, or use True dup in the same Toolbox group. Duplicating the layer in the timeline (Ctrl+D) doesn't do it: both layers point at the same comp, so editing one changes the other.

By hand:

1. Select the precomp in the Project panel and press Ctrl+D (Cmd+D). After Effects makes a copy of the comp.
2. Select the layer you want to change in the timeline.
3. Alt-drag (Option-drag on a Mac) the copy from the Project panel onto that layer. The layer's source is swapped, and its timing, transforms and effects stay.

One catch: precomps nested inside the copy are still shared with the original. If the thing you want to change lives two levels down, duplicate that inner comp too and swap it in the same way.

True dup duplicates a precomp as a separate, unlinked copy in one press, so you can change one without the other. As with the manual route, open the copy and check any precomps nested inside it before you edit.

When is it worth precomposing each layer in After Effects?

When each layer needs something only a precomp layer gives it:

• Its own time remap. Freeze or reverse one element without touching the rest.
• One effect on a combined result, such as a glow over a logo built from several parts.
• A slot to swap. One precomp per product shot or client logo means replacing the contents never disturbs the animation outside.
• Layouts. The workspace's Composition board lays selected precomp layers out as a presentation board, and Motion Showcases turns 2 to 20 selected layers into a looping 3D card showcase.

When it isn't: if all you want is to move several layers together, parent them to a null. It's lighter, and the layers stay in your main timeline where you can see them.

If you overdo it, unprecomposing in After Effects goes the other way, and Un-precomp empties up to 12 precomps at a time. After a big split the Project panel is the next mess; batch rename handles comps and project items as well as layers.

Does Precomp sep work on a Mac?

No. Precomp sep, True dup and the rest of Toolbox are in the mouzeclick workspaces, which are Windows only; the Mac app does not include them. On a Mac, use the manual steps above. Two parts of mouzeclick that do run on Mac can shorten them: a mouse button for Cmd+Shift+C, and mouzerun, one of the mouzeclick extensions, which turns a menu command, script, expression, preset or ease into a one-click button inside After Effects.

The workspaces come with every mouzeclick licence on Windows since 0.58.40, at no extra cost. For what else is in the After Effects panel, see the all-in-one After Effects extension guide. If you're deciding what to install, read the difference between a plugin, a script and an extension.

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