Preload Attribute
This table lists the preload behavior of different browsers and devices that support HTML5, at different settings of the preload attribute. For every setting and browser, we have indicated if the preload tag is followed.
| Browser | none | (omitted) |
|---|---|---|
| Firefox 20 | Yes | - |
| Chrome 26 | Yes | - |
| Safari 6 | Yes | - |
| Internet Explorer 9 | - | - |
| Internet Explorer 10 | Yes | - |
| Opera 12 | Yes | - |
| iOS 4 (iPhone) | -1 | - |
| iOS 5 (iPad) | -1 | - |
| iOS 6 (iPad) | -1 | - |
| Android 2.2 (HTC Legend) | Yes | Yes |
| Android 2.3 (HTC Desire) | Yes | Yes |
| Android 4.0 (Galaxy S2) | Yes | Yes |
| Android 4.1 (Nexus 7) | Yes | Yes |
| WinPho 7.5 (HTC Radar) | Yes | Yes |
- A 1B header ping is sent to the video file
See the HTML5 preload spec for a description of preload options and desired bahavior.
Test Setup
Our test video with the 'none' attribute is 02:20 at 270p. For Firefox and Opera, we used this encode (WebM, 19MB). For the other browsers and devices, we used this encode (MP4 16MB).
Our test video with the omitted attribute is 00:52 at 270p. For Firefox and Opera, we used this encode (WebM, 3MB). For the other browsers and devices, we used this encode (MP4 4MB).
We saved this page a few times with different values for the preload attribute. For obtaining data, we proxied each browser and device through the Charles web proxy:
- Chrome, Firefox, Internet Explorer and Safari are automatically proxied by Charles.
- Opera has proxy settings in Preferences » Advanced » Network » Proxy Servers.
- iOS, Android 2.3 and WinPho 7.5 each have proxy options in their WiFi settings.
- Android 2.2 has no proxy support. We refered to checking the serverlogs on this one.