the nuances of tagging categories
so, like, ao3 has different tag categories, such as rating, major warnings, relationships, characters, freeform, and so on. now, i know that a lot of people don’t realize there’s that much of a difference btwn the relationships, characters, and freeform tags and how that affects filtering, bc i fucking see you guys tagging shit as “minor or background relationships” followed by tagging the minor/background relationships in the relationships category, fucking clogging up those tags for people looking for fics featuring them. i fucking see that shit i’ve been on this website since mid-2016.
ahem. anyway, so the reason that tagging a ship as “minor beidou/ningguang” in the relationships category will make it show up when looking for “beidou/ningguang” is bc the relationships category of tags only concerns itself with which characters relate to each other in romantic or platonic ways.
i cannot stress this enough: it does not care how present the pairing is, only whether they relate to each other ROMANTICALLY or PLATONICALLY. the tag wranglers will make any “minor/past/one-sided” modifiers to a relationships category tag synonymous with just the regular version of the tag, hence why they will show up when searching through that tag.
the freeform tag category, on the other hand, CAN differentiate btwn “minor beidou/ningguang”, “established beidou/ningguang”, “married beidou/ningguang”, and so on and so forth, bc the freeform category is designed to just, like, differentiate these kinds of things.
if a fic is tagged “minor beidou/ningguang” in the freeforms category but NOT the relationships category, then anyone filtering “beidou/ningguang” in or out from the relationships category of the filters will not be affected by that fic. if someone is filtering “past beidou/ningguang” from the freeform or other category of filters, they will likewise not be affected.
this is bc of something called the filter_ids.
"what's a filter_ids" i don't have time to explain in full here; just know it's an old-fashioned ao3 thing of me to know. anyway, basically, ao3 filtering isn't word matching, and filter_ids are basically what allows us to filter particular tags and their canonical synonyms in or out. you can do a lot a lot of super cool, fine-grain filtering on ao3 if you know how to use them properly!
the relationships category form of a tag has a different filter_ids from the freeform variants (each of which has its own unique filter_ids, by the way— for example, filter_ids:48203638 refers to beiguang (relationships category), filter_ids:52238595 refers to “minor beiguang” (freeform category), filter_ids:60804856 refers to “married beiguang” (freeform category), and you get the idea): they can all be filtered independently from one another as a result.
anyway, it is typically considered to be good etiquette to put major pairings (ships that the fic actually places long-term focuses on) into the relationships category and then minor/background pairings into the freeforms category. consistently visible and relevant side pairings can admittedly be a bit of a grey area, but a good rule of thumb in my opinion is that it goes into the relationships category if someone looking for content featuring that ship will be satisfied with their ship’s role in the story, and it goes in freeform if it’s just, like, a tasty little side thing, but not really a whole Thing.