About caching

As After Effects displays a frame or compiles a RAM Preview, it places each of those displayed or compiled frames into a cache. Once the frames are cached, they display or play back quicker because they are now playing or displaying from RAM. Currently cached frames are designated by green bars in the time ruler; choose Show Cache Indicators from the Timeline window menu to toggle the cache indicators on and off.

Note: When you use OpenGL previews, After Effects does not cache frames until the preview is complete.

When you advance either sequentially or nonsequentially through frames in your composition, or play back using the Standard Preview option, each of the frames is compiled and placed into the cache, and the green bars appear in the Timeline at the point where the cached frame occurs. When you compile a RAM Preview, the frames you designate to be included in the preview are compiled, and the green bars appear in the time ruler to indicate which frames were cached. If you make a change to any of the cached frames in the composition, the cache purges only the frames affected by that change. You can also manually purge the entire cache.

Once the cache is full, and you continue to advance either sequentially or nonsequentially through frames in your composition, any additional frame added to the cache replaces the earliest cached frame in order to make room for the new frame. When you compile frames for RAM Previews, once the cache is full, After Effects ceases adding frames to the cache and the preview begins playback of only the frames that could fit in the cache. You can specify the size of the cache in the Cache preferences. The number of frames that can occupy the cache depends on the composition settings, layer sizes and several other variables.

To set Cache preferences:

1. Choose Edit > Preferences > Cache (Windows) or After Effects > Preferences > Cache (Mac OS.)
2. Set any of the options below:
• Enter an amount for Image Cache Size as a percent of the amount of installed RAM. (The default value is 60%; Adobe does not recommend values over 90%.) The amount you enter determines the maximum amount of memory After Effects uses for cached frames. The number of frames that RAM Preview displays is also limited by this setting: Increase it to get longer RAM Previews; decrease it if RAM Previews are jerky or halting because of virtual memory paging activity.
• Enter an amount for Maximum Memory Usage as a percent of the amount of installed RAM. (The default value is 120%; Adobe does not recommend values over 200%.) This setting limits the amount of memory After Effects can use. Increase the amount if insufficient memory errors occur. You can specify amounts greater than 100% because virtual memory is not limited to the amount of installed RAM.

To purge the cache:

Make sure that the Timeline window is selected, and choose Edit > Purge > Image Caches.