When inserting an image in a post, how to link the image to a resized URL instead of the full image URL?

Question

I'm using the classic editor and here are my default settings for images:

In a post, I want all inserted images to be linked to the medium size URL instead of the full sized URL, which appears to be how WP sets it when choosing link to 'Media File'.

Ideally, I want a way to set it for existing and future posts. So far I've found 2 possible ways:

1. The image_send_to_editor filter: I str_replace the $url with the medium size URL. This works for future images that are added to the posts but not for existing images.

2. The the_content filter: This would work for existing posts but I'm not sure if I should go with this.

Is there a better approach out there, and which do you recommend?

Answer 1

You can use wp_get_attachment_link(), function if you pass the size argument as medium you will get the medium size image link.
https://codex.wordpress.org/Function_Reference/wp_get_attachment_link