The twitter/the-algorithm repository hosts the open-source codebase for X's Recommendation Algorithm. Its primary purpose is to define the intricate set of services and jobs responsible for curating and serving feeds of posts and other diverse content across all X product surfaces, including the highly visible "For You Timeline," Search, Explore, and Notifications.

Developed predominantly in Scala, the repository features a sophisticated architecture built upon shared data, models, and software frameworks. Key architectural components include:

Data Services: Responsible for managing core post data, real-time user actions, and explicit/implicit user signals.
Recommendation Models: A diverse collection of models powering various aspects of the algorithm, such as community detection (SimClusters), knowledge graph embeddings (TwHIN), user reputation (Tweepcred), and trust & safety content moderation (which includes components written in Python).
Software Frameworks: Foundational tooling for building and serving content feeds (Product Mixer), handling streaming events (Recos Injector), managing embeddings, and high-performance model serving (such as navi, developed in Rust).

The algorithm's influence extends across critical user-facing features:

For You Timeline (FYT): This surface leverages various candidate sources (e.g., Search Index, User-Tweet-Entity Graph, Follow Recommendation Service) and multiple ranking models (Light Ranker, Heavy Ranker) to construct personalized feeds, followed by content mixing and visibility filters.
Recommended Notifications: This system utilizes dedicated services and ranking models (Pushservice, Pushservice Light Ranker, Pushservice Heavy Ranker) to deliver timely and relevant content recommendations directly to users via notifications.

This repository offers transparency into the mechanisms that drive content discovery and engagement on the X platform, reflecting a complex interplay of data processing, machine learning, and high-performance serving infrastructure.

Overview