Personal Ratings Summary (Beginning at Best)

Rank	Community	Key Feature
1	Tumblr	Empathetic, psychological/character theories, calm discussions.
2	TikTok	Video essays, short-form content, good for arguments/solid opinions.
3	YouTube	Essential for editing, scene packs, sometimes quality theories.
4	Reddit	Often misinformed, but useful for D&D information.
5	X	Hostile at times, good for short proofs, interviews, and Q&A.

Personal Ratings

(beginning at best)

TUMBLR
There are a lot of people who write from an empathetic place which results in a lot of psychological/character theories in blogs which helps develop larger plot theories later on-- you get hit with a lot of epiphanies here and it's constant. People post elaborate theories and based on evidence as well, and it's a lot calmer than the others I've mentioned.

Threads by Lucii Bug on Tumblr:
(Click below)
TIKTOK
Video essays, short-form content, edits, discussions in comment sections and lives. If your algorithm is set then you'll get to experience both sides of theory arguments which helps you form solid opinions. There are so many great theories about the plot/clues/headcanons/assumptions. People are generally nice, but a lot of toxic self-insert Mileven fans tarnish the experience, as well as Bylers who fetishize the main characters but claim they are "allies." This is a crazy ship war, by the way! Reach out if you want to know more because I've been a Byler shipper since 2017 and have seen the ups and downs of this fandom...
YOUTUBE
Usually a lot of people who are misinformed share content but why I ranked it high up is because it's essential for editing as it provides a home for them and scene packs which further help build and convey theories with evidence. Sometimes you can find some pretty quality inputs and theories, but majority of the time the good video essays are from the random editors/Tiktokers on Tiktok or reposted from Tiktok to TUMBLR, X, and reddit.
REDDIT
Theorists who don't really know what's going on all the time live on this platform— you'll occasionally come across a good one, but again, seldom. Mainly used for D&D information which can help create theories.
X
X, Formerly known as Twitter, has a really big Stranger Things community presence. There can be greater amounts of hostility, but overall it is a pretty fun community for Bylers or people who love keeping up with short proofs, snippets of cast/creator interviews, random observations, discussions, online friends, and nostalgia. Also very good for asking questions you're curious about where a google search simply won't do.

THE ARCHIVE

It is also worth mentioning the diverse branches of this fandom on fanfiction sites. These sites are typically based on fan theories or headcanons, which are concepts or character traits the fandom has collectively deemed true/potentially true/wishful thinking. They are ranked below by perceived writing quality:

AO3 (Archive of Our Own) Known for having "Wattpad writers on steroids," this platform generally hosts the most detailed, long-form, and complex works, often adhering closely to fan theories or alternate universes that are quite creative. More often than not, you'll find mischaracterization in any fanfics, but a lot of AO3 writers find strength in understanding the characters.
FanFiction.net A long-standing platform offering a wide variety of content, serving as a solid middle ground for story quality and length.
Wattpad Often described as the "pre-AO3 phase." It's typically the starting point for younger writers, featuring shorter, more immediate, and sometimes less edited content.