[wp-trac] [WordPress Trac] #58213: Increase default for `wp_omit_loading_attr_threshold` to 3

[WordPress Trac]

#58213: Increase default for `wp_omit_loading_attr_threshold` to 3
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 Reporter:  flixos90     |      Owner:  (none)
     Type:  enhancement  |     Status:  new
 Priority:  normal       |  Milestone:  6.3
Component:  Media        |    Version:
 Severity:  normal       |   Keywords:  needs-patch needs-unit-tests
  Focuses:  performance  |
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 The current default threshold for how many content images to skip lazy-
 loading on (which is just 1) has proven to be too strict: Many sites have
 more than 1 large image and potential LCP candidate visible above the
 fold, and due to the very conservative threshold here, those sites may end
 up lazy-loading their LCP image which negatively affects load time
 performance.

 Based on HTTP Archive data queried to get a better idea of this (see
 attached screenshot), a reasonable default value for the filter would be
 3. >70% of sites have up to 3 equal-sized images in the initial viewport,
 each of which ''could'' be the LCP image and therefore should not be lazy-
 loaded. Sites that have fewer than 3 images above the fold will not see a
 negative performance impact, they will only lose out on 1-2 images that
 may otherwise have been lazy-loaded to be loaded immediately, which is an
 acceptable tradeoff to get faster overall load time performance.

 While we could of course increase the default to even a higher number, the
 % of sites that use a specific number greater than 3 is much lower, e.g.
 to cover 80% of sites in total, the default threshold would need to be set
 to 8, which is excessive and would reduce the lazy-loading benefits too
 much for the majority of sites.

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Ticket URL: <https://core.trac.wordpress.org/ticket/58213>
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