[wp-trac] [WordPress Trac] #50756: Lazy-load iframes

[WordPress Trac]

#50756: Lazy-load iframes
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 Reporter:  flixos90                             |       Owner:  flixos90
     Type:  enhancement                          |      Status:  assigned
 Priority:  normal                               |   Milestone:  5.7
Component:  Media                                |     Version:
 Severity:  normal                               |  Resolution:
 Keywords:  has-patch has-unit-tests needs-dev-  |     Focuses:
  note                                           |
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Changes (by flixos90):

 * keywords:  has-patch has-unit-tests => has-patch has-unit-tests needs-
     dev-note
 * milestone:  Future Release => 5.7


Comment:

 With https://github.com/WordPress/wordpress-develop/pull/703 I've taken a
 first pass on a PR for this, including tests.

 The main use-case for iframes in WordPress content today is oEmbed, which
 automatically transforms e.g. URLs. Since that filter runs (with priority
 8) before `wp_filter_content_tags()` (priority 10) on `the_content`, no
 extra thinking was necessary to support those, it just works by adding
 `iframe` support to `wp_filter_content_tags()`.

 Note that not all oEmbed providers produce server-side `iframe` output.
 Furthermore, note that not all oEmbed `iframe` output contains `width` and
 `height` attributes which, like for images, are necessary to add a
 `loading` attribute in order to avoid content shifting.

 cc @azaozz

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Ticket URL: <https://core.trac.wordpress.org/ticket/50756#comment:2>
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