Fits makes differently sized versions of an After Effects comp so you can prepare wide, vertical, and square layouts from the same source. It is a free micro tool in Motion Dock.
Variants makes new comps. Pick a frame, choose how the content fits, then click Make 1 variant.
The five starting frames are 16:9, 9:16, 1:1, 4:5, and 4K. The highlighted frame is picked; the others are available to add.
Keep one source or build a new layout
The default Fill mode places your original comp inside each new frame and scales it to cover the frame. Fit keeps the whole source visible, with space around it when the shapes differ. Editing the original updates both kinds of variant.
Use Re-layout when you want copied layers you can adjust separately. It keeps layers near their original edges or center. Crop makes a copy and centers its existing content in the new size. The fitting guide explains which mode suits each job.
Change existing comps together
The Settings tab edits existing comps. Fill in only the values you want to change and review the list before applying.
Turn on Nested to include their precomps. Blank fields leave each comp's setting as it is.
Start with one new comp
Make a vertical variant from an open composition. The original keeps its size and layers. Each Make, Swap, or Apply action is one After Effects undo step.
Fits prepares compositions. It does not render or export them.