RAM and disk caches

As you work on a composition, After Effects temporarily stores some rendered frames and source images in RAM, so that previewing and editing can occur more quickly. After Effects does not cache frames that require little time to render. Frames remain uncompressed in the image cache. You can control how After Effects stores images by setting image-caching preferences. For information on preferences that affect the RAM cache, see Memory & Multiprocessing preferences.

After Effects also caches at the footage and layer levels for faster previews; layers that have been modified are rendered during the preview, and unmodified layers are displayed from the cache.

Blue bars in the Timeline panel mark frames that are cached to disk. Green bars mark frames that are cached to RAM.

Choose Show Cache Indicators from the Timeline panel menu to turn the cache indicators on and off. Showing the cache indicators decreases performance slightly.

When the image cache is full, any new frame added to the image cache replaces a frame cached earlier. When After Effects renders frames for RAM previews, it stops adding frames to the image cache when the cache is full and begins playing only the frames that could fit in the image cache.

If disk caching is enabled, After Effects can store rendered items to your hard disk when the RAM cache is full during standard previews. The disk cache is not used for RAM previews. As with the RAM cache, After Effects only uses the disk cache to store a frame if it’s faster to retrieve a frame from the cache than to rerender the frame.

For the best performance, select a folder that’s on a different physical hard disk than your source footage. If possible, the folder should be on a hard disk that uses a different drive controller than the disk that contains your source footage. The disk cache folder can’t be the root folder of the hard disk.

The Maximum Disk Cache Size setting specifies the number of megabytes of hard disk space to use. This setting should be at least 2 gigabytes (GB).

The RAM cache and disk cache are automatically purged when you quit After Effects.

To purge the RAM cache and disk cache, choose Edit > Purge > Image Caches.