Size videos correctly

When it comes to keeping your users happy, size matters:

When it comes to keeping your users happy, size matters:

  • Don’t serve videos with a larger frame size or higher quality than the platform can handle.
  • Don’t make your videos any longer than they need be.
  • Long videos can cause hiccups with download and seeking; some browsers may have to wait until the video downloads before beginning playback.

Check video size

The actual video frame size as encoded may be different from the video element dimensions (just as an image may not be displayed using its actual dimensions).

To check the encoded size of a video, use the video element videoWidth and videoHeight properties. width and height return the dimensions of the video element, which may have been sized using CSS or inline width and height attributes.

Ensure videos don’t overflow containers

When video elements are too big for the viewport, they may overflow their container, making it impossible for the user to see the content or use the controls.

Android Chrome screenshot, portrait: unstyled video element overflows viewport Android Chrome screenshot, landscape: unstyled video element overflows viewport

You can control video dimensions using JavaScript or CSS. JavaScript libraries and plugins such as FitVids make it possible to maintain appropriate size and aspect ratio, even for Flash videos from YouTube and other sources.

Use CSS media queries to specify the size of elements depending on the viewport dimensions; max-width: 100% is your friend.


  • Don't force element sizing that results in an aspect ratio different from the original video. Squashed or stretched looks bad.

For media content in iframes (such as YouTube videos), try a responsive approach (like the one proposed by John Surdakowski).


    .video-container {
        position: relative;
        padding-bottom: 56.25%;
        padding-top: 30px;
        height: 0;
        overflow: hidden;

    .video-container iframe,
    .video-container object,
    .video-container embed {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
View full sample


    <div class="video-container">
      <iframe src="//"
              frameborder="0" width="560" height="315">
View full sample

Updated on 2014-04-29


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