# amethyst/legion

High performance Rust ECS library

Repository: https://github.com/amethyst/legion
Canonical: https://ross.abutalabs.com/products/legion
Language: Rust
License: MIT
License Family: permissive
Topics: rust, ecs
Last push: 2021-12-30T19:05:52+00:00

## Health v2 (maintenance only)
Score: 23/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 0, release rhythm 8, longevity 100
- inputs: {"age_days": 2734, "days_push": 1707, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1718, forks 140 (observed 2026-08-28T04:05:26.531520+00:00)

## What it is
Legion is a high-performance Entity Component System (ECS) library for Rust, designed for game projects with minimal boilerplate. It provides worlds, entities, components, and expressive high-performance queries for bulk data access.

## Use cases
- build a game in Rust with an entity component system architecture
- manage thousands of game entities with position and velocity components
- run parallel systems over component data efficiently
- query and iterate entities by their component types
- prototype game logic without heavy boilerplate

## When to choose
- you are writing a Rust game or simulation and want a feature-rich, performant ECS
- you want minimal boilerplate when defining components and systems
- you need expressive queries and parallel iteration over entities

## When to avoid
- you need a full game engine with rendering, audio, and asset management (consider Bevy or Amethyst)
- you need a library under very active development, as the latest release dates to late 2021
- your project is not written in Rust

## Facets
- artifact type: library
- maturity: maintenance
- function: game-engine, concurrency
- domain: gaming-tools
- platform: rust, cross-platform
- tags: ecs, entity-component-system, game-development, rust

## Member repositories
- amethyst/legion (main) score 23

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:05:26.531520+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T03:34:09.678794+00:00, confidence not recorded.
  - readme: https://github.com/amethyst/legion (fetched 2026-08-28T04:05:26.531520+00:00, sha 003752f1a8bd)
  - registry_crates: https://crates.io/api/v1/crates/legion (fetched 2026-08-29T11:10:04.927658+00:00, sha 5d8b91c7025c)
- Data as of 2026-08-30T08:39:29.467469+00:00.