[wp-trac] [WordPress Trac] #55443: Create WebP sub-sizes and use for output

[WordPress Trac]

#55443: Create WebP sub-sizes and use for output
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 Reporter:  adamsilverstein                      |       Owner:
                                                 |  adamsilverstein
     Type:  enhancement                          |      Status:  assigned
 Priority:  normal                               |   Milestone:  6.1
Component:  Media                                |     Version:  6.0
 Severity:  normal                               |  Resolution:
 Keywords:  has-unit-tests needs-dev-note        |     Focuses:
  needs-docs needs-user-docs 2nd-opinion needs-  |  performance
  testing changes-requested                      |
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Comment (by adamsilverstein):

 > Q1) What happens on a site with 100GB of existing images when thumbnails
 are regenerated (wp media regenerate, by a plugin, or by woo-commerce)?
 If this doesn't "blow up large sites" I'll begrudgingly drop my constant
 pleas for an option.

 I took a look at this a bit more carefully:

 - `wp media regenerate` **deletes old thumbnails by default** unless you
 pass `--skip-delete`. You can also pass `--only-missing` to regenerate
 only for new or changed sizes, sizes with existing meta wouldn't be
 regenerated
 - `regenerate-thumbnails` plugin (no longer supported) by default "Skips
 regenerating existing correctly sized thumbnails" - meaning WebPs would
 only be generated for newly added sizes.
 - `regenerate-thumbnails-advanced` similarly only generates
 missing/changed sizes by default ("Don't redo existing").
 - `woocommerce` - as far as i can tell looking at the code only
 regenerates sizes that have changed dimensions, or new sizes.



 > Q2) Is anything being done to where WebP would actually benefit existing
 content (ie. old posts/pages written with the classic editor)?

 yes. by default, WordPress filters the content, so images inserted from
 the media library (not by URL) will get updated on the fly to newer
 subsizes, if you `wp media regenerate` older content should start using
 the new WebPs (and your old JPEGs will be deleted).

 >
 > Q3) How are the < 2% of browsers that don't support WebP going to be
 addressed (again, that's predominantly old iOS devices)

 using a tiny bit of feature dection JS on pages with WebPs we can swap out
 images for the smallest JPEG we have (possibly the original upload). The
 approach would be similar to https://github.com/WordPress/wordpress-
 develop/pull/3034

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Ticket URL: <https://core.trac.wordpress.org/ticket/55443#comment:176>
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