Let's Encrypt website screenshot

Let's Encrypt

Let's Encrypt is a free, automated, and open certificate authority run by the Internet Security Research Group affiliated with the Linux Foundation. It provides TLS certificates to secure the web, having issued billions of certificates to enable HTTPS for websites worldwide via the ACME protocol.

Let’s Encrypt publishes 7 APIs on the APIs.io network, including Account API, Authorization API, Certificate API, and 4 more. Tagged areas include Certificates, Linux Foundation, Security, TLS, and ACME.

Let’s Encrypt’s developer surface includes documentation, engineering blog, and 5 more developer resources.

🌐 Visit website 📡 Source on GitHub
35.2/100 thin ▬ flat Agent 22/100 agent aware Full breakdown ↓
scored 2026-08-05 · rubric v0.9.1
AccessFreemium
7 APIs
CertificatesLinux FoundationSecurityTLSACMEPKI

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-08-05 · rubric v0.9.1
Composite quality — 35.2/100 · thin
Contract Quality 12.9 / 25
Developer Ergonomics 2.2 / 20
Commercial Clarity 7.9 / 20
Operational Transparency 4.8 / 13
Governance 0.0 / 12
Discoverability 7.4 / 10
Agent readiness — 22/100 · agent aware
Machine-Readable Contract 18 / 18
Agentic Access Contract 10 / 10
MCP Server 0 / 12
Machine-Readable Auth 0 / 10
Idempotency 0 / 9
Stable Error Semantics 0 / 8
Request/Response Examples 0 / 7
Rate-Limit Signaling 7 / 7
Typed Event Surface 0 / 6
Agent Skills 0 / 5
Well-Known Catalog 0 / 4
Consent & Bot Identity 0 / 3
A2A Agent Card 0 / 8
Dry-Run / Simulate Mode 0 / 4
Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. This rating is computed from github.com/api-evangelist/lets-encrypt: open an issue to ask a question, or submit a pull request to add artifacts. Want it done for you? Prioritized profiling — $2,500 →

APIs 7

Individual APIs this provider publishes, each with its own machine-readable definition.

Let's Encrypt Account API

ACME account creation and management

Let's Encrypt Authorization API

Domain control authorizations

Let's Encrypt Certificate API

Issued certificate retrieval and revocation

Let's Encrypt Challenge API

Validation challenges (HTTP-01, DNS-01, TLS-ALPN-01)

Let's Encrypt Directory API

Discovery document listing ACME resources

Let's Encrypt Nonce API

Anti-replay nonces for JWS-signed requests

Let's Encrypt Order API

Certificate issuance orders

Scroll for all 7

Open Collections 1

Open, tool-agnostic API collections (OpenAPI-derived and Bruno).

Let's Encrypt ACME API

OPEN COLLECTION

Pricing Plans 1

Published pricing tiers and plan structures.

Lets Encrypt Plans Pricing

3 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Lets Encrypt Rate Limits

5 limits

RATE LIMITS

FinOps 1

Cost, billing, and metering signals for API financial operations.

Lets Encrypt Finops

FINOPS

Security Posture 2

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Lets Encrypt Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Lets Encrypt Vulnerability Disclosure

security.txt · contact published

SECURITY

Agentic Access 1

Recommended x-agentic-access execution contracts for AI agents.

Lets Encrypt Agentic Access

12 operations · 10 acting · 1 human-in-the-loop

12 operations · 10 acting

AGENTIC

Resources

Documentation 2

Reference material describing how the API behaves

Documentation
Documentation
 Specification
Specification

Agent Surfaces 1

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess
AgenticAccess

Build 1

SDKs, sample code, and the tooling you integrate with

GitHubOrg
GitHubOrg

Access & Security 2

Authentication, authorization, and security posture

VulnerabilityDisclosure
VulnerabilityDisclosure
 DomainSecurity
DomainSecurity

Company 1

The organization behind the API

Blog
Blog

Source (apis.yml)

apis.yml Raw ↑ 
aid: lets-encrypt
name: Let's Encrypt
description: Let's Encrypt is a free, automated, and open certificate authority run by the Internet Security Research Group
  affiliated with the Linux Foundation. It provides TLS certificates to secure the web, having issued billions of certificates
  to enable HTTPS for websites worldwide via the ACME protocol.
type: Index
accessModel:
  pricing: freemium
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Freemium
  confidence: medium
  source:
  - plans
  generated: '2026-07-22'
  method: derived
position: Consumer
access: 3rd-Party
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/lets-encrypt.png
tags:
- Certificates
- Linux Foundation
- Security
- TLS
- ACME
- PKI
created: '2026-03-16'
modified: '2026-05-19'
url: https://raw.githubusercontent.com/api-evangelist/lets-encrypt/refs/heads/main/apis.yml
specificationVersion: '0.19'
apis:
- aid: lets-encrypt:lets-encrypt-account-api
  name: Let's Encrypt Account API
  description: ACME account creation and management
  humanURL: https://letsencrypt.org/docs/
  baseURL: https://acme-v02.api.letsencrypt.org
  tags:
  - Account
  properties:
  - type: OpenAPI
    url: openapi/lets-encrypt-account-api-openapi.yml
  - type: Documentation
    url: https://letsencrypt.org/docs/
- aid: lets-encrypt:lets-encrypt-authorization-api
  name: Let's Encrypt Authorization API
  description: Domain control authorizations
  humanURL: https://letsencrypt.org/docs/
  baseURL: https://acme-v02.api.letsencrypt.org
  tags:
  - Authorization
  properties:
  - type: OpenAPI
    url: openapi/lets-encrypt-authorization-api-openapi.yml
  - type: Documentation
    url: https://letsencrypt.org/docs/
- aid: lets-encrypt:lets-encrypt-certificate-api
  name: Let's Encrypt Certificate API
  description: Issued certificate retrieval and revocation
  humanURL: https://letsencrypt.org/docs/
  baseURL: https://acme-v02.api.letsencrypt.org
  tags:
  - Certificate
  properties:
  - type: OpenAPI
    url: openapi/lets-encrypt-certificate-api-openapi.yml
  - type: Documentation
    url: https://letsencrypt.org/docs/
- aid: lets-encrypt:lets-encrypt-challenge-api
  name: Let's Encrypt Challenge API
  description: Validation challenges (HTTP-01, DNS-01, TLS-ALPN-01)
  humanURL: https://letsencrypt.org/docs/
  baseURL: https://acme-v02.api.letsencrypt.org
  tags:
  - Challenge
  properties:
  - type: OpenAPI
    url: openapi/lets-encrypt-challenge-api-openapi.yml
  - type: Documentation
    url: https://letsencrypt.org/docs/
- aid: lets-encrypt:lets-encrypt-directory-api
  name: Let's Encrypt Directory API
  description: Discovery document listing ACME resources
  humanURL: https://letsencrypt.org/docs/
  baseURL: https://acme-v02.api.letsencrypt.org
  tags:
  - Directory
  properties:
  - type: OpenAPI
    url: openapi/lets-encrypt-directory-api-openapi.yml
  - type: Documentation
    url: https://letsencrypt.org/docs/
- aid: lets-encrypt:lets-encrypt-nonce-api
  name: Let's Encrypt Nonce API
  description: Anti-replay nonces for JWS-signed requests
  humanURL: https://letsencrypt.org/docs/
  baseURL: https://acme-v02.api.letsencrypt.org
  tags:
  - Nonce
  properties:
  - type: OpenAPI
    url: openapi/lets-encrypt-nonce-api-openapi.yml
  - type: Documentation
    url: https://letsencrypt.org/docs/
- aid: lets-encrypt:lets-encrypt-order-api
  name: Let's Encrypt Order API
  description: Certificate issuance orders
  humanURL: https://letsencrypt.org/docs/
  baseURL: https://acme-v02.api.letsencrypt.org
  tags:
  - Order
  properties:
  - type: OpenAPI
    url: openapi/lets-encrypt-order-api-openapi.yml
  - type: Documentation
    url: https://letsencrypt.org/docs/
common:
- type: AgenticAccess
  url: agentic-access/lets-encrypt-agentic-access.yml
- type: VulnerabilityDisclosure
  url: security/lets-encrypt-vulnerability-disclosure.yml
- type: DomainSecurity
  url: security/lets-encrypt-domain-security.yml
- type: Documentation
  name: Let's Encrypt Documentation
  description: Official documentation for Let's Encrypt.
  url: https://letsencrypt.org/docs/
- type: GitHubOrg
  name: Let's Encrypt GitHub
  description: Source code and repositories for Let's Encrypt.
  url: https://github.com/letsencrypt
- type: Specification
  name: ACME RFC 8555
  description: IETF specification for the ACME protocol.
  url: https://datatracker.ietf.org/doc/html/rfc8555
- url: https://letsencrypt.org/feed.xml
  type: Blog
maintainers:
- FN: Kin Lane
  email: info@apievangelist.com