[wp-trac] [WordPress Trac] #56930: Block themes: improve omitting lazy-loading attribute on first content image/iframe

[WordPress Trac]

#56930: Block themes: improve omitting lazy-loading attribute on first content
image/iframe
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 Reporter:  adamsilverstein                      |       Owner:  flixos90
     Type:  defect (bug)                         |      Status:  closed
 Priority:  normal                               |   Milestone:  6.2
Component:  Media                                |     Version:  5.9
 Severity:  normal                               |  Resolution:  fixed
 Keywords:  has-patch has-unit-tests has-        |     Focuses:
  testing-info commit add-to-field-guide         |  performance
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Comment (by flixos90):

 I did some quick performance benchmarking for this feature.

 While we already have a more general
 [https://docs.google.com/spreadsheets/d/1LroIJoYz-
 O9CpfJzaiKYYMWJ7GbE5RZoW1rf1R4FqyA/edit#gid=996638482 Web Vitals
 comparison for WordPress 6.2 and 6.1], those tests were made without a
 post that contains an image, which is specifically something that this fix
 helps with (for block themes only).

 Doing a similar test with a block theme page with an image shows a notable
 **~19% LCP improvement in 6.2** (for content without an image it was only
 ~14%), and focusing on client-side performance specifically, the combined
 metric LCP - TTFB is improved by ~13% in 6.2 (for content without an image
 it was only ~3%).

 So it is fair to say that this is a major win for client-side performance
 for any block theme that uses a hero image.

 Here is the data:
 https://docs.google.com/spreadsheets/d/1n2fTB8DFGHpdrqIl9FP_Cjb7umPmidadjJChvbBRbXI/edit

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Ticket URL: <https://core.trac.wordpress.org/ticket/56930#comment:53>
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