Are Flexbox and vh height units not compatible in IE11?

Question

I'm trying to use a flexbox-based layout to get a sticky footer for my page. This works well in Chrome and Firefox, but in IE11 the footer sits just after my main content. In other words, the main content isn't stretched to fill all of the available space.

How can I get the main element to stretch in a flex layout when the containers height units are measured in vh in IE? I was looking to see if this behaviour is the result of a bug in the way IE implements the flexbox specs, but I couldn't find any mention of this problem elsewhere.

JSFiddle Demo

Answer 1

The issue isn't vh units but min-height

I found a semi-working CSS-only solution:

min-height: 100vh;
height: 100px;

The extra height will enable IE to fill the screen vertically even if the content is not tall enough. The drawback is that IE will no longer wrap the content if it's longer than the viewport.

---

Since this is not enough I made a solution in JS:

Detection

This function tests the bug: true means it's buggy.

function hasBug () {
    // inner should fill outer
    // if inner's height is 0, the browser has the bug

    // set up
    var outer = document.createElement('div');
    var inner = document.createElement('div');
    outer.setAttribute('style', 'display:-ms-flexbox; display:flex; min-height:100vh;');
    outer.appendChild(inner);
    (document.body || document.documentElement).appendChild(outer);

    // test
    var bug = !inner.offsetHeight;

    // remove setup
    outer.parentNode.removeChild(outer);

    return bug;
}

Fix

The fix consists of manually setting the height of the element in px

function fixElementHeight (el) {
    // reset any previously set height
    el.style.height = 'auto'; 

    // get el height (the one set via min-height in vh)
    var height = el.offsetHeight; 

    // manually set it in pixels
    el.style.height = height + 'px'; 
}

The element's height will be set to exactly the height of its content. height is used as a secondary min-height in IE, using the behavior observed in the CSS-only solution.

Usage

Once those two functions are defined, set it up this way:

if(hasBug()) {
    // fix the element now
    fixElementHeight(el);

    // update the height on resize
    window.addEventListener('resize', function () {
        fixElementHeight(el);
    });
}

Demo

function hasBug () {
    // inner should fill outer
    // if inner's height is 0, the browser has the bug

    // set up
    var outer = document.createElement('div');
    var inner = document.createElement('div');
    outer.setAttribute('style', 'display:-ms-flexbox; display:flex; min-height:100vh;');
    outer.appendChild(inner);
    (document.body || document.documentElement).appendChild(outer);

    // test
    var bug = !inner.offsetHeight;

    // remove setup
    outer.parentNode.removeChild(outer);

    return bug;
}

function fixElementHeight (el) {
    // reset any previously set height
    el.style.height = 'auto'; 

    // get el height (the one set via min-height in vh)
    var height = el.offsetHeight; 

    // manually set it in pixels
    el.style.height = height + 'px'; 
}

var output = document.getElementById('output');
output.innerHTML = hasBug()?'Browser is buggy':'Browser works correctly';


var el = document.getElementById('flex');

if(hasBug()) {
  // fix the element now
  fixElementHeight(el);

  // update the height on resize
  window.addEventListener('resize', function () {
    fixElementHeight(el);
  });
}

.half-screen {
  display:-ms-flexbox;
  display: flex;
  min-height: 50vh;

  padding: 10px;
  background: #97cef0;
}


.content {
  padding: 10px;
  background: #b5daf0;
}

The inner box should fill the outer box vertically, even if the browser is buggy.
<div class="half-screen" id="flex">
  <div class="content" id="output">
    Text
  </div>
</div>