I looked around, maybe I am not seeing it, but I wanted to ask if there was "OR" search functionality in e621.

Essentially like how it works on derpibooru, where 'x OR y' would give results that contained either or, and you could search for one tag or another in your favorites doing like 'faves, (x OR y)'

This would be super useful to know if it works here, because I search like that often.

~cat ~dog
Search for posts that are tagged either cat or dog (or both). May not work well when combined with other syntaxes.

From search options.

~cat ~dog feral ~bird fav:crocogator -rating:e
Returns posts that contain at least one of the following tags:
Cat, dog, bird
and also contains the tag feral
and is favorited by me
and is not rated as explicit

The behavior of the tilde modifier is interesting. It appears to respect other modifiers like "-" (the "not" modifier). It does not appear to respect meta-tags.

It appears that e621 considers ~ to be more like a "at least one of these" modifier - it will return posts that have at least one of the tags modified by it.

• So ~cat will return pictures with the cat tag, the same behavior as cat with no modifiers.

• ~cat ~dog will return pictures with either the cat or dog tags.

• female ~cat ~dog will return pictures with the female tag, which also contain either the cat or dog tags.

If you wanted to search for your favorites which contain some "x" or "y", you might try fav:JPone123 ~x ~y. Or, for more concrete example, maybe fav:JPone123 ~fluttershy_(mlp) ~applejack_(mlp).

It would be pretty cool if there were better tag-grouping or boolean support in e621, but at the same time I don't feel like it's really "missing" for any of my purposes, so I'm not going to be the one to make a feature request here. :3