How to disable WordPress from creating thumbnails?

These are some thoughts on disabling WordPress from creating multiple thumbnails, it might work for you and might not depends on the theme yo have, plugins etc …

– Turn off any plugins.
– Switch to your default theme.
– Set all image sizes to 0 in the Settings –> Media settings.

disable WordPress from creating thumbnails

This should keep WP from generating those extra thumbnails sizes. WP should creates only one additional thumbnail around 20-25Kb

If this doesn’t work for you, then either a plugin or the theme you are using is making some changes.

Some themes have functions like add_image_size, set_post_thumbnail_size or update_option('large_size_w', 500); in the functions.php file, so you will need to check that file.

hope it helps