How to remove the aditional thumbnails sizes

Hi all,

I installed the plugin “Simple image sizes” on my web when I was developing it, thinking i’d need a few more sizes.

Later I’ve realize it’s not something that helps the performance, it’s completely opposite since I mostly use PNG images, and thumbnails takes more disk space than original images. I’ve for example an image at 1920x3284px that takes 250kb, the thumbnails are bigger than 1mb.

Even when I set “Full Size” in gutemberg for those images, in mobile and in the lighthouse test it takes the thumbnail. It makes the URL performance fall dramatically.

I’ve try to delete the thumbnails in the uploads folder, but since wordpress think they’re here, the problem is bigger: image not found.

I’ve this on the wordpress media section:

https://i.postimg.cc/kR9mQrQB/thumbnails.png

If I delete the customized sizes, they appear again when I press “apply” button. I’ve also set 0x0px on the default wordpress sizes.

I’ve read that customized sizes are on functions.php, but those sizes are not in my theme’s file or child’s file. I really don’t know how to delete those customized sizes.

Thanks in advance