After Effects preview is slow or loops only a few seconds

Identify what is stopping

Save your project and note three things: the loop's start and end, whether it always stops at the same point, and whether a second pass is smoother. Keep the same composition and section while comparing settings; changing the scene at the same time makes the result hard to interpret.

Check the shortcut's range

Open Window > Preview. Select your actual shortcut in Shortcut; Spacebar and Numpad-0 can have different settings. Set Range to Work Area for a controlled comparison, and position that work area around the section you need. Check Play From as well.

If you enable Cache Before Playback, expect a wait while frames are prepared. That wait is different from a playback failure. Avoid resetting every shortcut before recording your current choices. Adobe explains these controls in its preview documentation.

Reduce the preview's workload

Try a lower preview resolution, such as Half, before reducing the composition's actual dimensions. Use a short section that still contains the troublesome effect or movement. Close unnecessary memory-heavy applications and pause other active previews.

Adobe's performance guide also recommends fast local source storage and reducing unnecessary processing. For diagnosis, compare a duplicate composition with one expensive effect temporarily disabled. Restore it before final output. This comparison can identify where to investigate; it is not a recommendation to remove part of the finished design.

Read the cache indicators in context

Green timeline marks identify frames in RAM; blue marks identify disk-cached frames. Adobe describes how available memory limits the frames held for a preview in its memory and storage guide.

Clearing caches forces affected frames to be calculated again. It therefore is not the first choice merely because the first pass is slow. Do not delete project media or operating-system folders to make room for a preview.

If the same section still fails

Record the exact After Effects version, OS, RAM, composition dimensions, preview settings, and the frame or error where progress stops. Note whether the same issue occurs in a simple composition without third-party effects. Use Adobe After Effects Help for the relevant support route.

This guide is based on Adobe documentation. We have not reproduced the issue in the app or measured performance gains.