Teslo | Open-source Elo rating package
William Grosset
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Posted Jan 12, 2026
Developed an open-source Elo rating package for multiplayer games, optimized for simplicity, correctness, and scalability (33K+ downloads).
Teslo is an open-source Elo rating package designed to make competitive ranking predictable and easy to integrate for multiplayer games.
The library provides a clean, well-tested TypeScript API for calculating Elo updates across multiplayer matches, including individual players and teams, while remaining flexible enough to support custom K-factors, matchmaking experiments, and different competitive formats. I focused heavily on correctness and developer experience, shipping comprehensive unit tests, clear documentation, and sensible defaults so teams could drop it into the browser or a Node.js backend with minimal setup.
Since launch, Teslo has grown to 33K+ downloads, with developers using it in live games and prototypes to power leaderboards, matchmaking systems, and progression mechanics. The project is fully open-source, actively maintained, and designed to be extensible as game rules and player populations evolve.
Technologies: TypeScript, Node.js, Jest
https://teslo.dev
Visit the website for more information: https://teslo.dev
Technologies: TypeScript, React, TailwindCSS, Next.js