I would like to change the image sizes for "medium" and "large".

I did change the sizes in Settings > Media

enter image description here

This however does not seem to have any effect on the settings I see when I edit or insert an image:

enter image description here

I did empty cache and reset the browser.

I also changed the theme's settings for the custom image size and content_width accordingly – but this does not have any influence on what options are displayed under Image Details.

add_image_size('full-width', 1600, 0, false);

if ( ! isset( $content_width ) ) $content_width = 1600;

Now I'm stuck – would appreciate any pointer… Thanks!

PS: I know there are plugins like Simple Image Sizes that could be handy – but I would like to try to do this 'the right way' (if that makes any sence).

2 Answers 2


Your image sizes need to be regenerated, as for the images to have different sizes they need to be cropped from the original and written to an actual file, whereas the settings only updates the settings, so will only affect future uploads. The Regenerate Thumbnails plugin can help with fixing this. The plugin allows you to regenerate the image sizes for all images or any number of specific individual images.


Solved: The new / custom sizes are only available for new images… 

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