How to Purge Cache to Speed Up Image Editing

During intensive image editing sessions, software stores temporary data—including undo states, clipboard items, and rendered previews—directly in your system's RAM and scratch disks. Over time, this data accumulates, causing brush lag, slow rendering, and frozen tools. This guide explains how to instantly purge cache memory within popular editing software and operating systems to restore real-time performance without restarting your computer.

Purge Cache in Adobe Photoshop

Photoshop provides a built-in purge utility that immediately frees up memory occupied by your editing history.

  1. Click on Edit in the top menu bar (or Photoshop on macOS).
  2. Hover over Purge.
  3. Choose the specific item to clear:
    • Clipboard: Deletes large copied pixel selections from memory.
    • Histories: Clears all previous undo states, freeing significant RAM.
    • All: Flushes the clipboard, undo history, and video cache simultaneously.
    • Video Cache: Deletes temporary preview files if working with timeline or video frames.

Note: Purging histories permanently removes the ability to use the Undo command for prior steps.

Clear Raw and Preview Caches in Lightroom

Adobe Lightroom maintains large cache files for fast image previews and Camera Raw processing. When these grow excessively large, performance drops.

  1. Go to Edit > Preferences (Windows) or Lightroom > Preferences (macOS).
  2. Open the Performance tab.
  3. Under Camera Raw Cache Settings, click Purge Cache.
  4. Under Video Cache Settings, click Purge Cache.
  5. Restart the catalog to apply the changes.

Clear Undo History in GIMP

If using GIMP, open image data and excessive undo steps can rapidly consume memory.

  1. Go to the Dockable Dialogs menu and select Undo History.
  2. Click the Clear Undo History button at the bottom of the panel to release held memory.
  3. Adjust your cache ceiling by navigating to Edit > Preferences > System Resources and decreasing the Minimal number of undo levels if memory issues persist.

Flush System-Level Cache (Windows and Mac)

If in-app purging does not resolve the latency, background system processes may be hogging resources.

  • On Windows: Press Ctrl + Shift + Esc to open the Task Manager. Locate non-essential background processes or hanging sub-processes from previous editor sessions and click End Task.
  • On macOS: Open Terminal and enter sudo purge, then press Enter. Provide your administrator password to force the operating system to clear inactive memory and disk caches.

Long-Term Adjustments to Prevent Lag

To avoid frequent manual purges, configure your software settings to manage memory more efficiently:

  • Reduce Undo States: Lower your maximum history states (e.g., in Photoshop, reduce from 50 to 20 under Preferences > Performance).
  • Allocate Dedicated Scratch Disks: Point your temporary storage to a fast internal NVMe or SSD with at least 50 GB of free space, rather than your primary operating system drive.
  • Optimize RAM Allocation: Ensure your editing application is assigned between 70% and 80% of total system RAM, leaving the remainder for background OS tasks.