Simplify Modifiers

In the options, the type of Modifiers to simplify can be selected.

For instance, if Subdivision Surface modifiers are needed in the scene, de-select it so they are left untouched when simplifying.

Tip

Subdivision Surface and other heavy modifiers are usually the biggest source of viewport slowdown. Keep them selected here unless you specifically need them while animating.

See the Execution Times page to measure which modifiers cost the most in your scene.