Login.gov Authentication API

openapi: 3.1.0
info:
  title: Login.gov OpenID Connect Authentication API
  version: 2026-01
  description: 'Login.gov is the U.S. federal government''s secure single sign-on service for public-facing

    government applications, operated by the General Services Administration''s Technology

    Transformation Services. This OpenAPI describes the OpenID Connect (OIDC) integration

    surface used by relying parties (service providers) to authenticate users at IAL1 (auth

    only) and IAL2 (identity-verified) assurance levels.


    Login.gov conforms to the iGov OpenID Connect Profile. Implicit flow is not supported.

    Client authentication uses private_key_jwt (preferred for web apps) or PKCE

    (preferred for native mobile apps).

    '
  contact:
    name: Login.gov Partner Support
    url: https://developers.login.gov
    email: partners@login.gov
  license:
    name: Public Domain (U.S. Government Work)
    url: https://www.usa.gov/government-works
servers:
- url: https://idp.int.identitysandbox.gov
  description: Sandbox (integration) environment
- url: https://secure.login.gov
  description: Production environment
tags:
- name: Authentication
  description: SAML SSO request endpoint.
paths:
  /api/saml/auth2026:
    get:
      tags:
      - Authentication
      summary: Initiate SAML SSO (HTTP-Redirect)
      operationId: samlSso
      description: 'Accepts a Base64-encoded, DEFLATE-compressed `SAMLRequest` via HTTP-Redirect.

        The user authenticates with Login.gov and the IdP responds with a signed SAML

        assertion POSTed to the SP''s Assertion Consumer Service URL.

        '
      parameters:
      - name: SAMLRequest
        in: query
        required: true
        description: Base64-encoded DEFLATE-compressed AuthnRequest.
        schema:
          type: string
      - name: RelayState
        in: query
        required: false
        description: Opaque value echoed back in the SAML response.
        schema:
          type: string
      - name: SigAlg
        in: query
        required: false
        description: Signature algorithm URI when the request is signed.
        schema:
          type: string
      - name: Signature
        in: query
        required: false
        description: Base64-encoded signature over the request.
        schema:
          type: string
      responses:
        '200':
          description: Login.gov sign-in UI is rendered to the end user.
        '302':
          description: Redirect to authentication challenge or to SP ACS with the signed SAML response.
components:
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      bearerFormat: opaque