# Cysharp/R3

The new future of dotnet/reactive and UniRx.

Repository: https://github.com/Cysharp/R3
Canonical: https://ross.abutalabs.com/products/r3
Language: C#
License: MIT
License Family: permissive
Last push: 2026-08-26T05:20:11+00:00

## Health v2 (maintenance only)
Score: 77/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 99, release rhythm 52, longevity 71
- inputs: {"age_days": 1000, "days_push": 7, "days_rel": 106, "gap_med": 299.0, "n_releases_24m": 3}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 3969, forks 182 (observed 2026-08-28T04:08:30.799815+00:00)

## What it is
R3 is a modern reimplementation of Reactive Extensions (Rx) for .NET, succeeding dotnet/reactive and UniRx with a redesigned core focused on in-memory event messaging. It supports many platforms including Unity, Godot, Avalonia, WPF, WinForms, WinUI3, MAUI, Blazor, and more, with frame-based operations and improved performance.

## Use cases
- handle event streams in C# applications
- replace UniRx in Unity game projects
- reactive UI bindings in WPF or Avalonia
- frame-based timing operations in game engines
- modern Rx alternative for .NET with better performance
- compose observable event pipelines without scheduler overhead

## When to choose
- building games or apps on .NET platforms needing reactive event handling
- migrating from UniRx or dotnet/reactive to a modern, faster Rx
- you need frame-based operations in Unity or Godot
- you want Rx aligned with modern C# features

## When to avoid
- you need backpressure and distributed reactive streams - use IAsyncEnumerable, Channels, or Reactive Streams instead
- single asynchronous operations - use async/await directly
- projects locked to the classic System.Reactive API surface

## Facets
- artifact type: library
- maturity: active
- function: middleware, concurrency, developer-tools
- domain: developer-tools, cross-platform, backend
- platform: dotnet, cross-platform, game-engine, windows
- tags: reactive-extensions, rx, unirx, csharp, event-streams, linq-to-events, game-engine, observables, game-development, web-server

## Member repositories
- Cysharp/R3 (main) score 77

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:08:30.799815+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 2026-08-29T18:24:22.511501+00:00, confidence not recorded.
  - readme: https://github.com/Cysharp/R3 (fetched 2026-08-28T04:08:30.799815+00:00, sha ccaf63894dc6)
- Data as of 2026-08-30T08:39:29.467469+00:00.