# Why does the operation lag when previewing?

When previewing, you can check the fps value in Menu-View-Show Statistics to check how many frames per second are transmitted when running the current scene; the fps value during previewing does not affect the actual rendering output result. 

If the fps value is lower than 20 when running the scene, there will be a lagging feeling; the fps value will be reduced when the graphics memory is high. You can check the current graphics memory usage by viewing Task Manager - Performance - GPU - View - Dedicated GPU Memory. 

If memory usage is high, consider using Smooth Mode during preview or combining it with ↓ content to optimize memory usage.

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> How to view and optimise video memory usage?