# http4s/http4s

A minimal, idiomatic Scala interface for HTTP

Repository: https://github.com/http4s/http4s
Canonical: https://ross.abutalabs.com/products/http4s
Homepage: https://http4s.org/
Language: Scala
License: Apache-2.0
License Family: permissive
Topics: scala, http, http-server, http-client, cats, fs2, typelevel
Last push: 2026-08-24T01:20:09+00:00

## Health v2 (maintenance only)
Score: 93/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 99, release rhythm 80, longevity 100
- inputs: {"age_days": 5287, "days_push": 10, "days_rel": 58, "gap_med": 42.5, "n_releases_24m": 9}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 2626, forks 814 (observed 2026-08-28T04:07:05.297693+00:00)

## What it is
Http4s is a minimal, idiomatic Scala library for building HTTP servers and clients, serving as Scala's equivalent to Rack, WSGI, WAI, and Servlets. It favors typeful, purely functional programming built on cats-effect and FS2 streaming, and cross-builds for Scala.js and Scala Native.

## Use cases
- build http services in scala
- serve rest apis with functional scala
- make http client requests from scala
- stream large payloads over http in constant memory
- implement websockets in scala
- share http code across jvm, js, and native

## When to choose
- you want a type-safe, purely functional http stack in Scala
- you already use cats-effect, fs2, or the Typelevel ecosystem
- you need streaming request/response bodies or websockets
- you want to cross-compile http code to Scala.js or Scala Native

## When to avoid
- you prefer imperative or non-functional Scala http frameworks
- you need a batteries-included full-stack framework rather than a minimal http interface
- your team is unfamiliar with cats-effect and effect systems

## Facets
- artifact type: library
- maturity: stable
- function: http-server, http-client, web-framework, middleware, routing, websocket, streaming
- domain: web-development, backend, apis
- platform: jvm, cross-platform
- tags: scala, cats-effect, fs2, typelevel, functional-http, scalajs, scala-native, functional-programming, web-server

## Member repositories
- http4s/http4s (main) score 93

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:07:05.297693+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 2026-08-30T02:19:47.303181+00:00, confidence not recorded.
  - readme: https://github.com/http4s/http4s (fetched 2026-08-28T04:07:05.297693+00:00, sha 65fa6dd40f63)
  - homepage: https://http4s.org/ (fetched 2026-08-29T10:02:42.411338+00:00, sha 8c9ff6221101)
  - site_page: https://http4s.org/changelog.html (fetched 2026-08-29T10:02:42.420543+00:00, sha 44828aa8deb8)
- Data as of 2026-08-30T08:39:29.467469+00:00.