A cookie is a mask that you place on a Light to create a shadow with a specific shape or color, which changes the appearance and intensity of the Light. Cookies are an efficient way of simulating complex lighting effects with minimal or no runtime performance impact. Effects you can simulate with cookies include caustics, soft shadows, and light shapes.
To apply a cookie to a Light in Unity, assign a texture to the Cookie field of a a Light component.
See render pipeline feature comparison for more information about support for cookies across render pipelines.
For Projects created in Unity 2020.1 or above, baked cookies are enabled for Baked Lights and Mixed Lights in the Progressive Lightmapper by default. For Projects created in versions of Unity prior to 2020.1, baked cookies are disabled for Baked Lights and Mixed Lights in the Progressive Lightmapper by default. This is to provide backwards compatibility.
You can toggle whether cookies are enabled for Baked Lights and Mixed Lights in the Progressive Lightmapper in the Editor settings window.