# ngtcp2/nghttp3

HTTP/3 library written in C

Repository: https://github.com/ngtcp2/nghttp3
Canonical: https://ross.abutalabs.com/products/nghttp3
Homepage: https://nghttp2.org/nghttp3/
Language: C
License: MIT
License Family: permissive
Topics: quic, http3, qpack, rfc9114, rfc9204, rfc9218, rfc9220, rfc9297
Last push: 2026-08-19T12:38:43+00:00

## Health v2 (maintenance only)
Score: 93/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 98, release rhythm 83, longevity 100
- inputs: {"age_days": 2854, "days_push": 14, "days_rel": 38, "gap_med": 46.5, "n_releases_24m": 15}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1135, forks 130 (observed 2026-08-28T04:03:43.317278+00:00)

## What it is
nghttp3 is a C implementation of HTTP/3 (RFC 9114) over QUIC and QPACK (RFC 9204). It is QUIC-transport-agnostic and supports extensions like extensible prioritization, WebSockets bootstrapping, and the ORIGIN extension.

## Use cases
- implement http3 in c
- add http/3 support to a server
- qpack header compression library
- build a quic-based http client
- integrate http3 into curl
- parse http3 frames

## When to choose
- you need a low-level, QUIC-implementation-agnostic HTTP/3 library in C
- you want RFC-compliant HTTP/3 with QPACK and extension support
- you are building a custom HTTP/3 client or server on top of your own QUIC stack

## When to avoid
- you want a complete HTTP/3 server or client out of the box
- you need server push, which is not supported
- you prefer a higher-level language binding or all-in-one QUIC+HTTP/3 stack

## Facets
- artifact type: library
- maturity: active
- function: http-server, http-client, serialization, networking
- domain: web-development, networking, developer-tools
- platform: windows, cpp, c
- tags: http3, quic, qpack, rfc9114, rfc9204, c-library, webtransport-adjacent, linux, macos

## Member repositories
- ngtcp2/nghttp3 (main) score 93

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:03:43.317278+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 2026-08-30T06:36:48.382149+00:00, confidence not recorded.
  - readme: https://github.com/ngtcp2/nghttp3 (fetched 2026-08-28T04:03:43.317278+00:00, sha 8dbe7d64bd7b)
  - homepage: https://nghttp2.org/nghttp3/ (fetched 2026-08-29T12:41:40.724576+00:00, sha 418fd323d3bd)
- Data as of 2026-08-30T08:39:29.467469+00:00.