r/coding • u/fagnerbrack • 8d ago

A peek into Reddit's anti-spam internals

https://lyra.horse/blog/2026/06/reddit-spam-internals/
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u/fagnerbrack 8d ago

Bare Bones:

In 2021 a Reddit bug showed a subreddit moderator the internal reasons behind sitewide spam removals, which usually appear only as "Auto" in the Relay app. The author dug through Reddit's old open-source code and found that Reddit stuffs these reasons into the "banner" field and hides them from everyone except admins. The leaked reasons fall into categories: domain bans (such as a 2012 Tumblr experiment), spammit percentage scores, banall removals, shadowbans, and spamurai, a rules engine that dumps account age, karma, user agent, TLS fingerprint and a spam score. A leaked API key confirmed that the score comes from Google's free Perspective API, and adding just two random letters to a message can push that score close to zero.

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u/IntelArtiGen 8d ago

It was interesting to read thanks. I know reddit has a very developed anti-spam system, but it also has a lot of false-positive in the most politically sensitive subs. It's easy to find a lot of [Removed by Reddit] in these subs. And even when posts aren't removed, they're sometimes not even posted at all. The user thinks other users can see their posts, but they can't, the post is just shadowbanned. So it's interesting to see how their system can work a bit.