Wordpress change default thumbnail size

Question

Is there a code that I can add to functions.php to change the default thumbnail size? I know that I can change the size in settings but I need a function that will do that automatically for my theme. I'm not referring to post thumbnails.

Answer 1

You can't change them but what you should do is register your own image sizes instead and use those in your theme. See add_image_size() for documentation. Then instead of using the built-in thumbnail sizes, just use that custom one you define in your theme.