# FluentValidation/FluentValidation

A popular .NET validation library for building strongly-typed validation rules.

Repository: https://github.com/FluentValidation/FluentValidation
Canonical: https://ross.abutalabs.com/products/fluentvalidation
Homepage: https://fluentvalidation.net
Language: C#
License: Apache-2.0
License Family: permissive
Last push: 2026-08-12T12:15:35+00:00

## Health v2 (maintenance only)
Score: 74/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 97, release rhythm 31, longevity 100
- inputs: {"age_days": 6100, "days_push": 21, "days_rel": 303, "gap_med": 169, "n_releases_24m": 4}
- flags: no_readme
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 9752, forks 1275 (observed 2026-08-28T04:10:37.064806+00:00)

## What it is
FluentValidation is a popular .NET library for building strongly-typed validation rules with a fluent interface. It lets developers define reusable, testable validation logic for models in C# applications.

## Use cases
- validate request models in ASP.NET Core APIs
- build reusable business rule validation in C#
- replace data annotations with fluent validation rules
- validate DTOs before persistence
- write unit-testable validation logic
- integrate validation into MediatR pipelines

## When to choose
- you're on .NET and need complex, strongly-typed validation rules
- you want validation logic that is easy to unit test and reuse
- data annotations are too limited for your business rules

## When to avoid
- you only need simple required-field checks that data annotations cover
- you're not working in the .NET ecosystem

## Facets
- artifact type: library
- maturity: stable
- function: form-handling, middleware
- domain: developer-tools, web-development, backend
- platform: dotnet, cross-platform
- tags: validation, fluent-api, csharp, strongly-typed

## Member repositories
- FluentValidation/FluentValidation (main) score 74

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:10:37.064806+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 2026-08-29T17:21:11.957390+00:00, confidence not recorded.
  - homepage: https://fluentvalidation.net (fetched 2026-08-29T08:20:43.118332+00:00, sha 7c1baea551c0)
- Data as of 2026-08-30T08:39:29.467469+00:00.