Created by Jeroen Wijering

« Back to The State of HTML5 Video

Preload Attribute

This table lists the preload behavior of HTML5 browsers, at different settings of the preload attribute. We tested against the following expectations:

  • If the preload attribute is set to none, the video is not fetched before a user starts playback, resulting in less data usage but slower startup.
  • If the preload attribute is omitted, the first part of the video is fetched on page load, resulting in instant playback when the user starts. Browsers should not pre-fetch the entire video.

See the HTML5 preload spec for more details.

Browser preload=none (no data) preload omitted (fast start)
Firefox for Desktop 20+ 20+
Chrome for Desktop 20+ 20+
Safari for Mac 5+ 5+
Internet Explorer for Windows 10+ 1 10+ 1
Opera for Desktop 12+ 12+
Safari for iOS 3+ - 2
Stock Browser for Android 4.0+ - 2
Chrome for Android 30+ - 2
Internet Explorer for WinPhone 7.5+ - 2
Firefox for Android 20+ - 2
  1. IE9 always pre-fetches the entire video, regardless of the preload setting.
  2. Mobile browsers never pre-fetch video data, regardless of the preload setting.

Test Setup

Our test video is 15:00 at 270p. For Firefox and Opera, we use this encode (WebM, 75MB). For the other browsers and devices, we use this encode (MP4 75MB). Here is the tag with preload=none attribute:

And here is the test tag without preload attribute:

For obtaining data, proxy your browser through a tool like the Charles web proxy:

  • Chrome, Firefox, Internet Explorer and Safari are automatically proxied by Charles.
  • iOS, Android and WinPhone have proxy options in their WiFi settings.