CSS adding border radius to an IFrame

Border radius isn't well supported or consistent yet. If you want the desired affect, try using DIV's around the element and use graphics instead, with an overflow of hidden in your CSS. You might want to look into the sliding doors tehnique if your iframe varies in height.

http://www.alistapart.com/articles/slidingdoors/

Hope this helps.

Good luck!

Put the iframe in a wrapper element and give the wrapping element this CSS property:

transform: translateY(0px);

.corner-wrapper {
  display: block;
  overflow: hidden;
  width: 300px;
  height: 150px;
  border-radius: 10px;
  transform: translateZ(0px);
  border: 3px solid #eee;
}

<div class="corner-wrapper">
    <iframe src="https://www.google.com/maps/embed?pb=!1m18!1m12!1m3!1d77935.71780117304!2d9.691260439866745!3d52.37964560033004!2m3!1f0!2f0!3f0!3m2!1i1024!2i768!4f13.1!3m3!1m2!1s0x47b00b514d494f85%3A0x425ac6d94ac4720!2sHannover!5e0!3m2!1sde!2sde!4v1458445807305" width="300" height="150" frameborder="0" style="border:0" allowfullscreen></iframe>
</div>

Use this property:

border: 4px solid #000;
-moz-border-radius: 15px;
border-radius: 15px;
overflow: hidden;

You can also do it like this:

<div style="padding:10px;background:#000;webkit-border-radius: 20px;-moz-border-radius: 20px;border-radius: 20px;width:560px;margin:0 auto;overflow:hidden;">
    <iframe src="http://www.youtube.com/embed/MOVIEID?fs=1&autoplay=1&loop=1&rel=0&border=0&modestbranding=1" width="560" height="315" frameborder="0"></iframe>
</div>

I have also included all the youtube options in the above example:

1: autoplay=1 (0/1 | automatic play movie)

2: loop=1 ( 0/1 looping on/off )

3: rel=0 ( hide related movies after movie ending, this does not always work)

4: border=0 (removes youtube border)

5: modestbranding=1 (removes youtube logo)