After Effects Preview Not Playing or RAM Preview Slow

How to fix it

Try these in order — the most common fix is first.

1. 1. Lower resolution and cache before playback

   Copy steps
   1. Set the Composition panel Resolution/Down Sample Factor to Half or Quarter
   2. In the Preview panel, set Resolution to Auto or a lower value
   3. For short work areas, set preview to cache before playback
   4. Shrink the work area to the section you are testing
   Did this fix it? Yes No

2. 2. Rebalance RAM and purge caches

   Copy steps
   1. Go to Edit > Preferences > Memory & Performance
   2. Adjust 'RAM reserved for other applications' (raise it if the system is starved)
   3. Choose Edit > Purge > All Memory & Disk Cache
   4. Restart After Effects and preview again
   Did this fix it? Yes No

3. 3. Check footage, power and display

   Copy steps
   1. Transcode heavy footage (MXF, long-GoP) to ProRes or DNxHR and relink
   2. Check OS power settings; some apps throttle the CPU during preview
   3. Try 60 Hz display refresh or a smaller AE window on 4K screens
   4. Update After Effects to the latest build and send logs via Help > Reveal Logging File if it persists
   Did this fix it? Yes No

Symptoms

RAM preview caches a few frames and stops, plays below real time, freezes, or the green cache bar never fills.

Why it happens

• Comp or preview resolution too high for the effects used
• Too little RAM left for other applications under Memory & Performance
• Heavy effects, recursive expressions or long-GoP footage (e.g. MXF/MPEG-2)
• Display refresh rate or very large 4K window slowing redraw
• Version-specific bugs (AE 22.5 stopped after ~5 frames, fixed in 23.0)

This guide also covers

• after effects preview not playing
• after effects ram preview slow
• ram preview not working after effects
• after effects preview stuttering

The same problem in other apps

All slow, laggy or resource-hungry guides →

• Blender Viewport Lag / Slow Viewport (Blender)

Other Adobe After Effects errors

• After Effects Render Failed in Media Encoder (Error Compiling Movie)
• After Effects Error: Crash / Can't Continue (GPU or Graphics Driver Issue)
• After Effects GPU Acceleration Not Available / Display Acceleration Disabled
• After Effects Missing Fonts or Missing Effects/Plugins
• After Effects Out of Memory / Unable to Allocate Memory Error
• After Effects Audio Out of Sync After Render
• After Effects Expression Error (Expression Disabled / Object of Type Found)
• After Effects Disk Cache Full or Won't Clear