Images in WordPress: How do they work?
summary
Uploads go through plupload and WordPress then runs WP_generate_attachment_metadata which calls WP_Image_Editor to produce thumbnail, small/medium/large and full sizes using ImageMagick (preferred) or GD. ImageMagick adds color profile support, PDF thumbnails and cut file sizes by ~50% (since 4.5/4.7), while generating all sizes in one HTTP request risks timeouts so originals land but sizes don’t. WordPress 5.3 adds save-as-generated / resume so partial size generation is recorded and can be retried instead of failing silently.
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chapters (17)
- 0:00Intro
- 1:09Sizes
- 2:28WP Image Editor
- 3:30Image Magic
- 4:29Color Profiles
- 5:04Size Reduction
- 5:38File Types
- 6:25Limitations
- 7:22Memory
- 8:14Dynamic
- 8:57Roadmap
- 9:08Safestate
- 10:19Gold Master
- 11:31HTTP Error
- 11:53Image Sizes
- 12:29Get involved
- 12:49Questions
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