How to authenticate in the Keycloak admin api?

So Keycloak has this admin api: https://www.keycloak.org/docs-api/22.0.1/rest-api/index.html#_overview

They do not mention what kind of authentication to use. I tried with Basic, but it does not work.

Access Token Request

https://datatracker.ietf.org/doc/html/rfc6749#section-4.3.2

Token Endpoint

POST http://localhost:8080/realms/{realm}/protocol/openid-connect/token

grant_type: password
username  : {admin username}
password  : {admin password}
client_id : admin-cli

Demo

1 Install Docker Desktop for Windows or Mac

https://www.docker.com/products/docker-desktop/

2 Launch Keycloak by docker-compose

Save as docker-compose.yml

version: '3.8'

services:
  postgres:
    image: postgres:15.6
    container_name: postgres_db
    volumes:
      - postgres_data:/var/lib/postgresql/data
    environment:
      POSTGRES_DB: keycloak
      POSTGRES_USER: keycloak
      POSTGRES_PASSWORD: password

  keycloak_web:
    image: quay.io/keycloak/keycloak:24.0.3
    container_name: keycloak_web
    environment:
      KC_DB: postgres
      KC_DB_URL: jdbc:postgresql://postgres:5432/keycloak
      KC_DB_USERNAME: keycloak
      KC_DB_PASSWORD: password

      KC_HOSTNAME: localhost
      KC_HOSTNAME_STRICT: false
      KC_HOSTNAME_STRICT_HTTPS: false

      KC_LOG_LEVEL: info
      KC_METRICS_ENABLED: true
      KC_HEALTH_ENABLED: true
      KEYCLOAK_ADMIN: admin
      KEYCLOAK_ADMIN_PASSWORD: admin
    command: start-dev
    depends_on:
      - postgres
    ports:
      - 8080:8080

volumes:
  postgres_data:

docker compose up -d

3 Get master token by Postman

Download and install Postman

POST http://localhost:8080/realms/master/protocol/openid-connect/token

In body tab Select x-www-form-urlencoded

Master's admin credential username is admin, password is admin.

grant_type: password
username: admin
password: admin
client_id: admin-cli

In Tests tab

const jsonData = JSON.parse(responseBody);
postman.setEnvironmentVariable("master-token", jsonData.access_token);

Press Send button

4 Call Admin API by Postman

Get reamls list

GET http://localhost:8080/admin/realms

In Authorization tab, Select Bearer Token and enter this text in Token editor control

{{master-token}}

You can see the realms list in the response Body

Note

The master token is valid for only 60 seconds as default.

You can extend more time for debugging purposes.

By Browser, open this URL

http://localhost:8080

Login using the master credential username is "admin" and password is "admin"