But all other values of PRELOAD vary in how much video data is downloaded. Luckily, preload='none' has consistent behavior across all browsers: nothing is buffered.
Observation #2: The amount of video preloaded varies across the major desktop browsers. As shown, that also does not cause any video download on mobile devices. When I saw this I decided to add a test for the AUTOPLAY attribute. Instead, the video doesn’t start downloading until the user initiates playback. The VIDEO spec calls the preload values “hints”, so it makes sense that mobile browsers would choose not to preload anything in order to save on data costs. Observation #1: Mobile devices don’t preload anything.
HTML5 VIDEO DOWNLOAD CHROME FULL
You can see the full results in Browserscope. It was very cool.) A subset of major browsers is shown in Table 1. (There were some race conditions in the test page that I resolved after an awesome realtime, tweet-driven debug session with voluntary testers. In order to gather results across various browsers I connected the test page to a Browserscope user test and tweeted asking people to run the test page. The final result is the number of seconds that are buffered (preloaded). JavaScript measures how much of the video is buffered.
Clicking on the various test links changes the state of the PRELOAD attribute. I created an HTML5 Video test page based on Philippe’s test page. Specifying the empty string is the same as specifying “auto”. preload='none' From the spec, “Hints to the UA that the user is not expected to need the video, or that minimizing unnecessary traffic is desirable.” preload='metadata' “Hints to the UA that the user is not expected to need the video, but that fetching its metadata (dimensions, first frame, track list, duration, and so on) is desirable.” preload='auto' “Hints to the UA that optimistically downloading the entire video is considered desirable.” preload or preload='' The preload attribute is specified but no value is given. The VIDEO PRELOAD attribute has the following possible states: no preload attribute Preload is not specified. Maybe its default behavior is to preload aggressively. Since the amount of video on the Web is growing (more details in a future post), I wondered if the VIDEO tag’s preload behavior could account for that. At last week’s HTML5 Developer Conference I attended Philippe Le Hegaret‘s session on “Video in the Open Web Platform”.