# dunglas/vulcain

🔨 Fast and idiomatic client-driven REST APIs.

Repository: https://github.com/dunglas/vulcain
Canonical: https://ross.abutalabs.com/products/vulcain
Homepage: https://vulcain.rocks
Language: Go
License: AGPL-3.0
License Family: copyleft
Topics: api, http2, server-push, rest-api, rest, graphql, reverse-proxy, vulcain, vulcain-server, hacktoberfest, early-hints, preload, http3, hypermedia-api, http2-push, caddy
Last push: 2026-08-15T09:04:16+00:00

## Health v2 (maintenance only)
Score: 92/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 97, release rhythm 81, longevity 100
- inputs: {"age_days": 2550, "days_push": 18, "days_rel": 46, "gap_med": 73, "n_releases_24m": 8}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 3593, forks 102 (observed 2026-08-28T04:08:11.251457+00:00)

## What it is
Vulcain is a protocol and reference gateway server (a Caddy web server module written in Go) that uses Preload hints, 103 Early Hints, and HTTP/2 Server Push to create fast, client-driven REST APIs. It can be placed in front of any existing API, supporting hypermedia formats and legacy APIs documented via OpenAPI.

## Use cases
- speed up a REST API by pushing related resources to clients
- put a gateway in front of an existing API to add preload and early hints support
- avoid overfetching and underfetching without switching to GraphQL
- map relations in a legacy non-hypermedia API using an OpenAPI spec
- serve a hypermedia API like JSON-LD, HAL, or JSON:API with HTTP/2 push
- reduce latency for API clients on HTTP/2 and HTTP/3 connections

## When to choose
- you have a REST or hypermedia API suffering from over/under-fetching or n+1 round trips
- you want GraphQL-like resource selection while keeping plain HTTP semantics, caching, and logs
- you want a drop-in reverse proxy that upgrades any existing API without changing backend code
- you already use Caddy or API Platform and want native HTTP/2 push and Early Hints

## When to avoid
- your clients or intermediaries do not support HTTP/2 or HTTP/3
- you need a fully managed API gateway with auth, rate limiting, and analytics built in
- your team prefers GraphQL-style query languages over HTTP header-based resource selection
- AGPL-3.0 licensing is incompatible with your distribution model

## Facets
- artifact type: service
- maturity: active
- function: http-server, api-framework, middleware, proxy, routing
- domain: apis, web-development, backend, performance
- platform: go, windows, self-hosted
- tags: http2, http3, server-push, early-hints, preload, rest-api, hypermedia, reverse-proxy, caddy, openapi, gateway-server, api-gateway, linux, macos, docker, web-server

## Member repositories
- dunglas/vulcain (main) score 92

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:08:11.251457+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 2026-08-29T18:33:50.177687+00:00, confidence not recorded.
  - readme: https://github.com/dunglas/vulcain (fetched 2026-08-28T04:08:11.251457+00:00, sha 7881e1e96168)
  - homepage: https://vulcain.rocks (fetched 2026-08-29T09:27:12.380507+00:00, sha f38b32689c10)
  - site_page: https://vulcain.rocks/docs/help (fetched 2026-08-29T09:27:12.388479+00:00, sha 8d53e3c907f9)
  - site_page: https://vulcain.rocks/docs (fetched 2026-08-29T09:27:12.382838+00:00, sha a39ad701c761)
  - site_page: https://vulcain.rocks/docs/gateway/openapi (fetched 2026-08-29T09:27:12.384840+00:00, sha 5ac9a637b3fb)
  - site_page: https://vulcain.rocks/docs/gateway/caddy (fetched 2026-08-29T09:27:12.386670+00:00, sha ee14cddcbfd5)
- Data as of 2026-08-30T08:39:29.467469+00:00.