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 API contracts indexed 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.

The Let’s Encrypt catalog on APIs.io includes 1 Spectral governance ruleset.

Let’s Encrypt’s developer surface includes documentation, engineering blog, and 10 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

23.7/100 emerging ▬ flat Agent 17/100 agent aware Front door AI 1/6 silent Heartbeat 100/100 alive Full breakdown ↓
scored 2026-11-13 · rubric v0.28.0 · Show this score on your site →

AccessFreemium

1 published contract

Certificates Linux Foundation Security TLS ACME PKI

What this lets a business do 1

Business capabilities this provider's published APIs can perform, derived from its own contracts. Browse all capabilities →

Cybersecurity Management

BC-620

Certificate

POST /acme/cert/{certId} POST /acme/revoke-cert

Kin Score

Kin Score How this is scored →
scored 2026-11-13 · rubric v0.28.0

Composite quality — 23.7/100 · emerging

Contract Quality 7.7 / 19

Developer Ergonomics 1.8 / 15

Access Clarity 1.0 / 15

Operational Transparency 2.1 / 10

Contract Governance 1.2 / 9

Discoverability 5.0 / 8

Regulatory Posture 1.8 / 15

Create-or-Update Ergonomics 0.0 / 10

Agent readiness — 17/100 · agent aware

Machine-Readable Contract 18 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 0 / 6

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

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Pagination 5 / 5

Distinct Operations 3 / 3

MCP Tool Quality 6 / 6

Regulatory Posture applies to this provider. Its tags matched the Horizontal (data, software, accessibility, platform) regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.

Create-or-Update Ergonomics applies to this provider. This API accepts writes, so it carries 10 points of the composite. It is scored from the published contracts themselves: whether a caller can create-or-update in one call, whether the write accepts a key the caller already holds, and whether the response says which branch ran. Without that, every write needs a search-and-branch in front of it, and the first time that check is skipped a duplicate record is created. Scored against the observed mean rather than raw — a provider at the catalog average is unchanged by this facet, not penalised by it.

The six quality facets above are damped to 75 points between them, because the conditional facet above carries the other 25. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 75% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

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Agent readiness — checks not met, largest first (exact, from this profile):

MCP Server +12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship Ask about this →
Machine-Readable Auth +10 pts — a served openid-configuration/oauth-authorization-server carrying `issuer` (served), else the securitySchemes class in the provider OpenAPIs — bound (mutualTLS, DPoP, Signature) > negotiable (oauth2 authorizationCode/clientCredentials, openIdConnect) > bearer (http bearer, apiKey) Ask about this →
Idempotency +9 pts — OpenAPI mutating operations declare an idempotency key — a header, a request-body property, or a named de-duplication token whose own description says so (verified); else common[].type matches /idempoten/i (documented) Ask about this →
Stable Error Semantics +8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes Ask about this →
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0 Ask about this →
Request/Response Examples +7 pts — share of operations carrying request/response examples; else an Examples / Code Samples link Ask about this →

10 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Access Clarity scores 6.4 — up to +18.7 composite points Ask about this →
Developer Ergonomics scores 11.9 — up to +17.6 composite points Ask about this →
Contract Quality scores 40.8 — up to +14.8 composite points Ask about this →

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

Not sure how this applies to your stack? Ask about any one item. Kin Lane reads every question, looks at your profile and your situation, and replies with what a fix would take — scoped to that one area, priced up front, yours whether you ship it or not. Ask a question →

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from the provider profile at artifacts.apis.io/lets-encrypt/apis.yml: open an issue on github.com/api-evangelist/lets-encrypt to ask a question or point us at an artifact you publish. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

Markets this provider is in provisional

The Kin Score Market layer reads a provider inside its market: its position, and how deep its integrations go. Depth is only comparable within a position. Provisional and unweighted: not part of the Kin Score or agent readiness.

Market	Position	Depth	Registered MCP server	Declares compatibility
PKI and Encryption (certificate authorities, key management)	standard	40.9 (thin)	-	-

Registered MCP server and declares compatibility are report only — not weighted. Undeclared means we found nothing we can read, so there is no number: we never infer integrations.

Standards implemented 1

Standards this provider implements or carries. De facto ones are profiled and measured by the API Commons; formal ones come from the standards directory and are linked by the provider's own tags. The evidence column says how each claim was established — not that it was made.

OpenAPI

measured — observed by APIs.io (published)

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 8

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

Let's Encrypt ACME Account API

OPEN COLLECTION

Let's Encrypt ACME API

OPEN COLLECTION

Let's Encrypt ACME Account Authorization API

OPEN COLLECTION

Let's Encrypt ACME Account Certificate API

OPEN COLLECTION

Let's Encrypt ACME Account Challenge API

OPEN COLLECTION

Let's Encrypt ACME Account Directory API

OPEN COLLECTION

Let's Encrypt ACME Account Nonce API

OPEN COLLECTION

Let's Encrypt ACME Account Order API

OPEN COLLECTION

Scroll for all 8

Let's Encrypt API pricing

Not yet checked against Let's Encrypt's own pricing page. Compiled by API Evangelist on 2026-05-04; confirm before you rely on a figure. A free plan or tier is listed.

Plan	Price
Free freemium	Free
Professional paid	Free
Enterprise enterprise	—

Plan details, limits and sources →

Rate limits

Free Tier Default: 10 requests per minute
Free Tier Monthly Quota: 1000 requests per month
Professional Tier Default: 100 requests per minute

Compiled by API Evangelist, not yet checked against Let's Encrypt's documentation. All 5 limits →

Pricing Plans 1

Published pricing tiers and plan structures.

Let's Encrypt Plans Pricing

3 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Let's Encrypt Rate Limits

5 limits

RATE LIMITS

FinOps 1

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

Let's Encrypt Finops

FINOPS

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs. Counts are the severity each rule declares, not results of running them.

Let's Encrypt API Rules

59 rules · 57 error-severity 1 warn-severity 1 info-severity

SPECTRAL

Security Posture 2

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

Let's Encrypt Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Let's Encrypt Vulnerability Disclosure

security.txt · contact published

SECURITY

Agentic Access (API Evangelist recommendations) 1

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

Let's Encrypt Agentic Access

12 operations · 7 acting · 1 human-in-the-loop

12 operations · 7 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

Operate 1

Status, limits, changes, and where to get help

RateLimits

RateLimits

Commercial 2

Pricing, plans, and the legal terms of use

Plans

Plans

FinOps

FinOps

Company 2

The organization behind the API

Website

Website

Blog

Blog

Other 1

Properties that don't map to a standard resource type

CapabilityMap

CapabilityMap

Source (apis.yml)

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
deliveryModel:
  model: unknown
  open_source: false
  commercial: false
  callable_host: true
  label: Delivery model not determined — needs a product licence on record
  confidence: low
  source:
  - openapi
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: freemium
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Freemium
  confidence: low
  source:
  - plans
  - security
  generated: '2026-11-13'
  method: derived
position: Consuming
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: '0.23'
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: Plans
  url: plans/lets-encrypt-plans-pricing.yml
- type: RateLimits
  url: rate-limits/lets-encrypt-rate-limits.yml
- type: FinOps
  url: finops/lets-encrypt-finops.yml
- type: CapabilityMap
  url: capabilities/lets-encrypt-capability-edges.yml
  name: Let's Encrypt Business Capability Map
- type: Website
  url: https://www.letsencrypt.org/
- 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

Let's Encrypt API — frequently asked questions

Does Let's Encrypt have an API?

Yes. APIs.io lists 7 APIs from Let's Encrypt, including Let's Encrypt Account API, Let's Encrypt Authorization API and Let's Encrypt Certificate API, and 4 more.

Is there an OpenAPI specification for the Let's Encrypt API?

Yes. APIs.io indexes 7 OpenAPI specifications for Let's Encrypt, each linked for download from this page.

How much does the Let's Encrypt API cost?

APIs.io lists 3 pricing plans for Let's Encrypt, with each plan's price, limits and inclusions under Pricing on this page.

Is the Let's Encrypt API ready for AI agents?

Let's Encrypt has a Kin Score of 23.7 out of 100 (emerging) and an Agent Readiness score of 17.2 (agent-aware), scored by API Evangelist on 2026-11-13.

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apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
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