Usage:

Very simple to use just press SHIFT+W and slide your mouse to the right to turn on UV Checkers or to the left to turn OFF UV Checkers.

Adjusting scale of checkers:

To adjust the scale of UV checkers use the 'Add UV Grid Textures' from the N-Panel.

Or Swipe down after Shift+W.

Using Custom Checker Texture:

Specify the path to your own checker texture in the preferences to use that instead of the default one.