Vertical centering flexbox overlay in iOS safari

Question

I have the following code for my flexbox overlay

.overlay-content-wrapper {
  display: -webkit-flex;
  display: flex;
  position:fixed;
  height: 100%;
  width: 100%;
  top: 0;
  z-index: 999;
    background-color: rgba(0, 0, 0, 0.6);
    padding: 8px;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
}

.overlay-content {
    padding: 8px;
    min-height: 10px;
    min-width: 10px;
    margin: auto;
    background-color: #fff;
    border-radius: 8px;
    border: 1px solid #a5a5a5;
    position: relative;
}

<div class="overlay-content-wrapper"><div class="overlay-content">Some content</div></div>

In Chrome it works perfectly but in iOS safari (v6 simulator) it doesn't center vertically. What do I need to change to get it to work?

Answer 1

After digging around for a while I discovered that iOS safari supports one of the old syntaxes with teh webkit prefix (given its market share it's surprising more flexbox tutorials/tools don't include the old syntax... but hey ho).

So here is my final CSS which should work in every browser that supports some version of flexbox and falls back to just horizontal centering in other browsers.

.overlay-content-wrapper {
  display: -webkit-box; /* OLD - iOS 6-, Safari 3.1-6 */
  display: -moz-box; /* OLD - Firefox 19- (buggy but mostly works) */
  display: -ms-flexbox; /* TWEENER - IE 10 */
  display: -webkit-flex;
  display: flex;
  -webkit-box-align: center;
  -webkit-flex-align: center;
  -ms-flex-align: center;
  -webkit-align-items: center;
  align-items: center;
  position:fixed;
  height: 100%;
  width: 100%;
  top: 0;
  z-index: 999;
  background-color: rgba(0, 0, 0, 0.6);
  padding: 8px;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}

.overlay-content {
    padding: 8px;
    min-height: 10px;
    min-width: 10px;
    margin: auto;
    background-color: #fff;
    border-radius: 8px;
    border: 1px solid #a5a5a5;
    position: relative;
}