Extend background gradient across body without background-attachment: fixed

Question

I want to have a background gradient, e.g.

background: linear-gradient(to bottom, rgba(0, 0, 0, 0.3), rgba(2, 126, 174, 0.9))

on the body of my document which extends across the entire height of the body - and scrolls with the body.

Using

background-attachment: fixed;

I get the entire height (of the viewport), but it, well, stays fixed.

background-attachment: scroll;

gets me the scrolling, but then it just extends across the viewport height.

Any way to get both?

Edit:

As Boltclock pointed out, I do get the expected behavior with 'background-attachment: scroll' on a basic test page.

With

<body>
   <div id="stretch">Content</div>
</body>

and

  body {
     background: linear-gradient(to bottom, rgba(0, 0, 0, 0.3), rgba(2, 126, 174, 0.9));
  }

  #stretch {
     height: 2000px;
  }

everything works fine: The gradient extends across the entire body (and the body is 2000px tall), and scrolls with the content.

Then I add

  html, 
  body {
     height: 100%;
  }

This is something which the basic template the page is based on does.

In order to get the body to expand again, I add

  height: auto;

and the body is back to 2000px height.

However, the gradient remains at the HTML height - and repeats then.

What am I missing here?

background-attachment: scroll is the default. If the body is taller than the viewport, your gradient declaration alone should be enough, unless I'm missing something. — BoltClock
You're right: On a bare-bones test page, the gradient expands to fill the entire body. Need to look what else in my CSS is causing this as a side effect. — gzost

BoltClock BoltClock · Accepted Answer · 2013-11-20T03:00:55

This happens because of the way gradient backgrounds are sized according to their containers (this includes both html and body), as well as the calculations used in determining the dimensions of html and body respective to the viewport.

I've actually written about something similar before in an answer to another question. Yours is a little different, so I'll quote the relevant portion first:

Backgrounds have special behavior when applied to body and/or html. When you apply a background to body without touching html, what happens is that the body background gets propagated to the viewport, and that background acts as if it were declared on html:

For documents whose root element is an HTML HTML element or an XHTML html element: if the computed value of ‘background-image’ on the root element is ‘none’ and its ‘background-color’ is ‘transparent’, user agents must instead propagate the computed values of the background properties from that element's first HTML BODY or XHTML body child element. The used values of that BODY element's background properties are their initial values, and the propagated values are treated as if they were specified on the root element.

In your case, if the template that you're using doesn't specify any backgrounds for html or body, then this background propagating behavior is what causes the gradient to take the height of html instead of body.

To fix this you need to reset the height value for the html element only, and assign min-height instead:

  html {
     height: auto;
     min-height: 100%;
  }

This removes the height constraint on the html element, allowing the gradient to stretch along with the contents of your page, while keeping it at least as tall as the viewport if the page doesn't have enough content (if that's not important, you don't need to set min-height).

Extend background gradient across body without background-attachment: fixed

2 Answers