# letsencrypt/boulder

An ACME-based certificate authority, written in Go.

Repository: https://github.com/letsencrypt/boulder
Canonical: https://ross.abutalabs.com/products/boulder
Language: Go
License: MPL-2.0
License Family: copyleft
Topics: boulder, go, acme, certificate-authority, tls, lets-encrypt, ca, pki, rfc8555
Last push: 2026-08-26T21:33:55+00:00

## Health v2 (maintenance only)
Score: 95/100 (v2, computed 2026-09-03T02:39:23.370411+00:00)
- activity 99, release rhythm 87, longevity 100
- inputs: {"age_days": 4274, "days_push": 7, "days_rel": 8, "gap_med": 7, "n_releases_24m": 102}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 5742, forks 646 (observed 2026-08-28T04:09:28.415217+00:00)

## What it is
Boulder is the Go implementation of an ACME-based certificate authority that powers Let's Encrypt. It automates domain validation and issuance/revocation of TLS certificates via the RFC 8555 ACME protocol, structured as separate gRPC-connected components.

## Use cases
- run a private ACME certificate authority
- issue TLS certificates automatically via ACME
- self-host a Let's Encrypt-like CA
- test ACME client implementations against a real CA
- automate certificate issuance and revocation for internal domains

## When to choose
- you need to operate your own ACME-compliant CA at scale
- you want a battle-tested, production-proven ACME server implementation
- you need automated domain validation and certificate lifecycle management

## When to avoid
- you just need TLS certificates for your own servers - use Let's Encrypt directly with an ACME client like Certbot
- you need a simple internal PKI without ACME - tools like step-ca or smallstep may be simpler
- you are not prepared to run a complex multi-component distributed service

## Facets
- artifact type: service
- maturity: active
- function: security, http-server, rpc, api-framework
- domain: security, backend, apis, developer-tools
- platform: go, self-hosted
- tags: acme, certificate-authority, pki, tls, rfc8555, lets-encrypt, x509, linux, docker

## Member repositories
- letsencrypt/boulder (main) score 95

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:09:28.415217+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 2026-08-29T17:53:20.982127+00:00, confidence not recorded.
  - readme: https://github.com/letsencrypt/boulder (fetched 2026-08-28T04:09:28.415217+00:00, sha ebfd735a246a)
- Data as of 2026-08-30T08:39:29.467469+00:00.