About the Subreddit Atlas

A map of NSFW Reddit communities, positioned by who comments where.

What This Is

This site is a network-analysis project. Each dot is an NSFW subreddit, and two subreddits sit near each other when they share commenters. No text from the communities is used to compute the layout. These communities are image-heavy and text-sparse, so the words they contain carry little signal about how they relate to one another. Who participates where turns out to carry that signal instead: the map recovers regional communities, kink neighborhoods, and language groupings purely from overlapping participation.

How the Map Is Built

For each subreddit I count which authors commented there during the 2024 calendar year, then binarize that to commented-or-not so that power users cannot dominate. From the resulting author-by-subreddit incidence matrix I compute subreddit co-occurrence, reweight it with positive pointwise mutual information (PPMI) to correct for community size, reduce it to 150 dimensions with a truncated SVD, and project to two dimensions with UMAP. Clusters come from HDBSCAN, and each cluster label is generated automatically from the subreddit names it contains using c-TF-IDF. One caveat worth stating: UMAP preserves local neighborhoods, not global distances, so how far apart two regions sit on screen is not a calibrated measure of how unrelated they are.

Data Source and Scope

The underlying data comes from the Arctic Shift per-subreddit archives, distributed through Academic Torrents. The map covers a few thousand of the most active public NSFW subreddits, using comments from the 2024 calendar year only. Accounts with bot-like names or bot-like activity patterns are filtered out before anything is counted.

What Is and Is Not Collected

The pipeline reads metadata only: author names, subreddit names, timestamps, and counts. Comment bodies, images, and URLs are never read out of the archives or written to any output. The published map contains no usernames at all. What you can see here is limited to subreddit names, aggregate commenter and subscriber counts, derived 2D coordinates, and each subreddit's public description.

Browsing Without the Map

Every mapped community also has a plain page listing its most similar subreddits by shared commenters, reachable from the directory of all mapped subreddits.

Removal Requests

If you moderate a subreddit shown on this map and would prefer it not be listed, email atlasafterdark@proton.me from an account that can plausibly speak for the community, and I will remove it. The map is rebuilt periodically, so removals are applied as an exclusion list rather than a one-time edit.

Supporting the Site

The site is free, has no ads, and sells nothing. If you find it interesting and want to help cover hosting and domain costs, you can chip in at liberapay.com/atlasafterdark.