How to add a full page background in html?

Question

I want a full page background

Answer 1

You can use CSS.
This is for color:
body {
background-color: black;
}

This is for image:
body {
background-image: url (source);
}

Answer 2

JTLZ thanks a lot for answering my questions

Answer 3

And then you have to add background-size:cover;