reveal js stretch background image to fit

Question

I'm trying to get the background image in my reveal js presentation to adjust its aspect ratio to fit the screen. Changing the size seems simple enough via

data-background-size=...

but I can't find anywhere that shows me how to make the image stretch to fit the screen

Answer 1

You can do it manually entering two parameters: data-background-size="800px 600px" for example.

Answer 2

This stretches the image to fit the slide, keeping its aspect ratio:

data-background-size="contain"

The attribute is mentioned in the Backgrounds section of the documentation.

For possible values of data-background-size, see the MDN documentation.