Welcome to the X For You Feed Algorithm
The For You feed algorithm retrieves, ranks, and filters posts from two sources: in-network content (from accounts you follow) and out-of-network content (discovered through ML-based retrieval). Both sources are combined and ranked together using Phoenix, a Grok-based transformer model that predicts engagement probabilities for each post.Overview
Understand how the For You feed works
Architecture
Explore the system architecture and components
Phoenix ML System
Learn about the Grok-based transformer models
API Reference
Browse the complete API documentation
Key Features
The X For You feed algorithm is built on several innovative design principles:Grok-Based Transformer
Uses transformer architecture from the Grok-1 open source release, adapted for recommendation systems
Candidate Isolation
Special attention masking ensures candidates can’t attend to each other during ranking
Multi-Action Prediction
Predicts probabilities for likes, replies, reposts, clicks, and more
Two-Stage Pipeline
Retrieval narrows millions of candidates to thousands, then ranking orders the final feed
Core Components
The system is built from several key components:Home Mixer
Orchestration layer that assembles the For You feed
Phoenix
ML component for retrieval and ranking with Grok-based transformers
Thunder
In-memory post store and real-time ingestion pipeline
Candidate Pipeline
Reusable framework for building recommendation pipelines
Design Philosophy
The system relies entirely on the Grok-based transformer to learn relevance from user engagement sequences. No manual feature engineering for content relevance.