[wp-trac] [WordPress Trac] #42438: Add support for preload links (similar to resource hints)

[WordPress Trac]

#42438: Add support for preload links (similar to resource hints)
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 Reporter:  nico23                        |       Owner:  swissspidy
     Type:  defect (bug)                  |      Status:  assigned
 Priority:  normal                        |   Milestone:  5.0
Component:  Script Loader                 |     Version:  4.9
 Severity:  normal                        |  Resolution:
 Keywords:  needs-unit-tests needs-patch  |     Focuses:
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Comment (by westonruter):

 For the preloading of images, this seems to be largely blocked by the
 implementation [https://www.chromestatus.com/feature/5164259990306816
 srcset and imgsizes attributes on link rel=preload] in browsers. Since
 images in WordPress almost always get served with `sizes` and `srcset`, it
 doesn't seem feasible to preload the image since we don't know which image
 size will be used, and the browser could very well preload the wrong image
 and waste bandwidth. In fact, when I tried adding preloading for the
 header image in Twenty Seventeen, I got an warning in DevTools:

 > The resource … was preloaded using link preload but not used within a
 few seconds from the window's load event. Please make sure it has an
 appropriate `as` value and it is preloaded intentionally.

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Ticket URL: <https://core.trac.wordpress.org/ticket/42438#comment:12>
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