[wp-trac] [WordPress Trac] #48477: Add a hook before creating image sub-sizes

[WordPress Trac]

#48477: Add a hook before creating image sub-sizes
-------------------------------------------------+-------------------------
 Reporter:  GregLone                             |       Owner:  (none)
     Type:  enhancement                          |      Status:  new
 Priority:  normal                               |   Milestone:  Future
                                                 |  Release
Component:  Upload                               |     Version:  5.3
 Severity:  normal                               |  Resolution:
 Keywords:  has-patch 2nd-opinion needs-dev-     |     Focuses:
  note                                           |
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Changes (by ozgursar):

 * keywords:  has-patch needs-testing 2nd-opinion needs-dev-note => has-
     patch 2nd-opinion needs-dev-note


Comment:

 == Patch Testing Report

 Patch Tested: https://github.com/WordPress/wordpress-develop/pull/9453

 === Environment
 - WordPress: 7.0-alpha-61215-src
 - PHP: 8.2.29
 - Server: nginx/1.29.4
 - Database: mysqli (Server: 8.4.7 / Client: mysqlnd 8.2.29)
 - Browser: Chrome 144.0.0.0
 - OS: macOS
 - Theme: Twenty Twenty-One 2.7
 - MU Plugins: None activated
 - Plugins:
   * Code Snippets 3.9.4
   * Test Reports 1.2.1

 === Steps taken
 1. Add the following snippet to `functions.php` or via Code Snippets
 plugin


 {{{
 add_action('wp_before_make_subsizes', function($new_sizes, $file,
 $image_meta, $attachment_id) {
     error_log("=== wp_before_make_subsizes HOOK FIRED ===");
     error_log("Attachment ID: " . $attachment_id);
     error_log("File: " . $file);
     error_log("Sizes to create: " . implode(', ',
 array_keys($new_sizes)));
     error_log("==========================================");
 }, 10, 4);
 }}}

 2. Add an image to Media
 3. Ensure `WP_DEBUG` and `WP_DEBUG_LOG` are enabled in `wp-config.php`
 4. Check `/wp-content/debug.log` to confirm the hook is running as
 expected
 5. When I uploaded a random image, the following lines are logged:


 {{{
 [01-Feb-2026 12:30:30 UTC] === wp_before_make_subsizes HOOK FIRED ===
 [01-Feb-2026 12:30:30 UTC] Attachment ID: 98
 [01-Feb-2026 12:30:30 UTC] File: /var/www/src/wp-
 content/uploads/2026/02/images.jpg
 [01-Feb-2026 12:30:30 UTC] Sizes to create: medium, large, thumbnail,
 medium_large, 1536x1536, 2048x2048, post-thumbnail
 [01-Feb-2026 12:30:30 UTC] ==========================================

 }}}

 6. ✅ Patch is solving the problem

 === Expected result
 - We are expecting `wp_before_make_subsizes` hook to run before creating
 image sub-sizes when an image is uploaded.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/48477#comment:16>
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