- Resource not referenced from the DOM. By default, your application’s DOM for is traversed for
- Multiple page loads. If users commonly go through two page loads in your app, but only the second page load uses the resource, you may want to schedule the resource for prefetching in every page load to make sure that it gets fetched in the first page load, thus making the second load faster.
The resource must properly return the following HTTP headers when requested by the client (if the headers are specified at all):
- Content-Type - Currently supported content types are
- Content-Length - Only the largest resources will be prefetched; if the size of the resource is not specified, it will be assumed to be 1K, which is unlikely to be large enough to be prefetched.
- Cache-Control - if this is set to
private, the resource will be ignored.
- Vary - if this is set, the resource will be ignored.
- Expires/Last-Modified - if there is too short a time between these two values, if only one is specified, or there is too short a time between the current time and one of these values, then the resource will be ignored.