X Algorithm: Writing Posts That Get Ranked

A single source of truth for writing on X, derived directly from the open-sourced For You algorithm. No folklore, no growth-hack myths — only what the actual ranker, retrieval system, and content classifiers reward or punish.

How the Feed Actually Works

Every For You impression is the output of this pipeline:

Sources                Filters               Scoring                 Selection
─────────              ───────               ───────                 ─────────
Thunder (in-network)   age, vf, muted        Phoenix transformer     top-K by score
Phoenix (OON ANN)      blocks, dedupe        → P(19 actions)         author diversity
ads / wtf / prompts    seen/served           weighted sum            ads blender
                       subscription gate     OON multiplier

Two ways into a user's feed: