For context on rule 34 you can separate groups of tags with "( ~ )" so you can get results with either combinations of both tag groups, for instance

"( Spider_man ~ peter_parker ) ( Human_torch ~ Johnny_Storm )" here are 2 super heroes and their secret identities, by putting the search like this I will get either combination of the Character on the left with the character on the right, since some posts only have certain tags, a post might have the peter_parker tag but not the spider_man one and vice versa, this way I can better filter posts and get more results with what I want, same way I would be able to search for posts here with " lagomorph, rabbit and/or hare" tags since some posts only include one of them while also searching for both "bovine and/or bovid" or "crocodile, alligator, and/or crocodilian" tags so it sorts the Bunnies and the Bulls (or gators) without making a mess and showing results with only 1 of the searched groups instead of 2

You can kind of use your blacklist for this, but doesn't work too well.
There's no proper way to do it on the site. There are tools to do it locally using the database export though, and if I remember correctly there's at least one browser extension for it.

Ah yes topic #40732

scth said:
You can kind of use your blacklist for this, but doesn't work too well.
There's no proper way to do it on the site. There are tools to do it locally using the database export though, and if I remember correctly there's at least one browser extension for it.

Ah yes topic #40732

welp, I'm using mobile so I'm cooked, also author said that the tool is broken

tay_mizami said:
welp, I'm using mobile so I'm cooked, also author said that the tool is broken

The author of that tool also had a pull request up for this a while ago, but things fell through. However, there's a new PR up picking up where that one left off that's looking like it'll get added, provided enough people take interest and have the time to review it before I give up on it. It's always been a want, but there's never been enough vocal demand for it to be pushed up the chain of priorities; at least while enough people with the time and motivation to do it is working on it.

BTW, where did they say it's broken? Nevermind, I apparently forgot how to read

IT'S (almost) HERE! This feature is now live on e926 and - provided nothing explodes - will then be added to e621. The tag cheatsheet hasn't been updated yet possibly because I completely forgot to mention we should do that, but you can check the syntax here and, if it isn't clear enough there, play with a live demo for it here (just change the "Test String" to the query you want, & hover over the colored text; the "Group" names tell you what the server will view it as, with "subquery" being the subsearch. Nested groups work (e.g. ~( aaa -( ~bbb ~ccc ) ) ~( ddd eee ) ), but the tester won't do the same highlighting for things inside a subquery).