# fabulous-dev/Fabulous

Declarative UI framework for cross-platform mobile & desktop apps, using MVU and F# functional programming

Repository: https://github.com/fabulous-dev/Fabulous
Canonical: https://ross.abutalabs.com/products/fabulous
Homepage: https://fabulous-dev.github.io/Fabulous/
Language: F#
License: Apache-2.0
License Family: permissive
Topics: declarative-ui, fabulous, fsharp, mvu
Last push: 2026-09-03T00:27:46+00:00

## Health v2 (maintenance only)
Score: 88/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 100, release rhythm 67, longevity 100
- inputs: {"age_days": 3131, "days_push": 0, "days_rel": 9, "gap_med": null, "n_releases_24m": 1}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1270, forks 120 (observed 2026-09-03T02:15:11.821821+00:00)

## What it is
Fabulous is a declarative UI framework for .NET that lets developers build cross-platform mobile and desktop applications in F# using the Model-View-Update (MVU) architecture. It supplies the application core, state handling, and declarative DSL, while rendering through pluggable backends such as .NET MAUI (Fabulous.MauiControls) and Avalonia (Fabulous.Avalonia).

## Use cases
- build cross-platform mobile apps with F#
- declarative UI framework for .NET desktop applications
- MVU / Elm-architecture state management for apps
- single codebase for iOS, Android, macOS and Windows
- testable application logic with pure update functions
- functional programming alternative to Xamarin/MAUI XAML

## When to choose
- Your team knows F# and prefers a functional, declarative programming model for app development
- You want MVU-style explicit state transitions that make update logic easy to reason about and unit test
- You are already in the .NET ecosystem and want one declarative codebase across mobile and desktop via MAUI or Avalonia

## When to avoid
- Your team works primarily in C# or other .NET languages rather than F#
- You need extensive third-party native control libraries or heavy platform-specific UI customization beyond what the MAUI/Avalonia bindings expose
- You require commercial vendor support; Fabulous is a community-built, sponsorship-funded project

## Facets
- artifact type: framework
- maturity: active
- function: mobile-framework, desktop-framework, state-management, ui-components
- domain: mobile-development, desktop-applications, cross-platform, frontend
- platform: cross-platform, windows, dotnet
- tags: mvu, elm-architecture, fsharp, declarative-ui, dotnet, maui, avalonia, functional-programming, mobile, desktop, android, ios, macos

## Member repositories
- fabulous-dev/Fabulous (main) score 88

## Provenance
- Observed fields: from GitHub, fetched 2026-09-03T02:15:11.821821+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 2026-08-30T05:03:37.823190+00:00, confidence not recorded.
  - readme: https://github.com/fabulous-dev/Fabulous (fetched 2026-09-03T02:15:11.821821+00:00, sha 975c9120a093)
  - homepage: https://fabulous-dev.github.io/Fabulous/ (fetched 2026-08-29T12:15:16.687793+00:00, sha 2709af35addd)
- Data as of 2026-08-30T08:39:29.467469+00:00.