Configuring the hostname

Learn how to configure the frontend and backchannel endpoints exposed by Keycloak.

Server Endpoints

Keycloak exposes different endpoints to talk with applications as well as to allow accessing the administration console. These endpoints can be categorized into three main groups:

  • Frontend

  • Backend

  • Administration Console

The base URL for each group has an important impact on how tokens are issued and validated, on how links are created for actions that require the user to be redirected to Keycloak (for example, when resetting password through email links), and, most importantly, how applications will discover these endpoints when fetching the OpenID Connect Discovery Document from realms/{realm-name}/.well-known/openid-configuration.

Frontend

The frontend endpoints are those accessible through a public domain and usually related to authentication/authorization flows that happen through the front-channel. For instance, when an SPA wants to authenticate their users it redirects them to the authorization_endpoint so that users can authenticate using their browsers through the front-channel.

By default, when the hostname settings are not set, the base URL for these endpoints is based on the incoming request so that the HTTP scheme, host, port, and path, are the same from the request. The default behavior also has a direct impact on how the server is going to issue tokens given that the issuer is also based on the URL set to the frontend endpoints. If the hostname settings are not set, the token issuer will also be based on the incoming request and also lack consistency if the client is requesting tokens using different URLs.

When deploying to production you usually want a consistent URL for the frontend endpoints and the token issuer regardless of how the request is constructed. In order to achieve this consistency, you can set either the hostname or the hostname-url options.

Most of the time, it should be enough to set the hostname option in order to change only the host of the frontend URLs:

bin/kc.[sh|bat] start --hostname=<host>

When using the hostname option the server is going to resolve the HTTP scheme, port, and path, automatically so that:

  • https scheme is used unless you set hostname-strict-https=false

  • Use the standard HTTP ports (e.g.: 80 and 443) if a proxy is set or use the port you set to the hostname-port option

However, if you want to set not only the host but also a scheme, port, and path, you can set the hostname-url option:

bin/kc.[sh|bat] start --hostname-url=<scheme>://<host>:<port>/<path>

This option gives you more flexibility as you can set the different parts of the URL from a single option. Note that the hostname and hostname-url are mutually exclusive.

Backend

The backend endpoints are those accessible through a public domain or through a private network. They are used for a direct communication between the server and clients without any intermediary but plain HTTP requests. For instance, after the user is authenticated an SPA wants to exchange the code sent by the server with a set of tokens by sending a token request to token_endpoint.

By default, the URLs for backend endpoints are also based on the incoming request. To override this behavior, set the hostname-strict-backchannel configuration option by entering this command:

bin/kc.[sh|bat] start --hostname=<value> --hostname-strict-backchannel=true

By setting the hostname-strict-backchannel option, the URLs for the backend endpoints are going to be exactly the same as the frontend endpoints.

When all applications connected to Keycloak communicate through the public URL, set hostname-strict-backchannel to true. Otherwise, leave this parameter as false to allow client-server communication through a private network.

Administration Console

The server exposes the administration console and static resources using a specific URL.

By default, the URLs for the administration console are also based on the incoming request. However, you can set a specific host or base URL if you want to restrict access to the administration console using a specific URL. Similarly to how you set the frontend URLs, you can use the hostname-admin and hostname-admin-url options to achieve that.

Most of the time, it should be enough to set the hostname-admin option in order to change only the host of the administration console URLs:

bin/kc.[sh|bat] start --hostname-admin=<host>

However, if you want to set not only the host but also a scheme, port, and path, you can set the hostname-admin-url option:

bin/kc.[sh|bat] start --hostname-admin-url=<scheme>://<host>:<port>/<path>

Note that the hostname-admin and hostname-admin-url are mutually exclusive.

To reduce attack surface, the administration endpoints for Keycloak and the Admin Console should not be publicly accessible. Therefore, you can secure them by using a reverse proxy. For more information about which paths to expose using a reverse proxy, see the Using a reverse proxy Guide.

Example Scenarios

The following are more example scenarios and the corresponding commands for setting up a hostname.

Note that the start command requires setting up TLS. The corresponding options are not shown for example purposes. For more details, see Configuring TLS guide.

Exposing the server behind a TLS termination proxy

In this example, the server is running behind a TLS termination proxy and publicly available from https://mykeycloak.

Configuration:
bin/kc.[sh|bat] start --hostname=mykeycloak --proxy=edge

Exposing the server without a proxy

In this example, the server is running without a proxy and exposed using a URL using HTTPS.

Keycloak configuration:
bin/kc.[sh|bat] start --hostname-url=https://mykeycloak

It is highly recommended using a TLS termination proxy in front of the server for security and availability reasons. For more details, see the Using a reverse proxy guide.

Forcing backend endpoints to use the same URL the server is exposed

In this example, backend endpoints are exposed using the same URL used by the server so that clients always fetch the same URL regardless of the origin of the request.

Keycloak configuration:
bin/kc.[sh|bat] start --hostname=mykeycloak --hostname-strict-backchannel=true

Exposing the server using a port other than the default ports

In this example, the server is accessible using a port other than the default ports.

Keycloak configuration:
bin/kc.[sh|bat] start --hostname-url=https://mykeycloak:8989

Relevant options

Type Default

hostname

Hostname for the Keycloak server.

CLI: --hostname

Env: KC_HOSTNAME

hostname-admin

The hostname for accessing the administration console.

Use this option if you are exposing the administration console using a hostname other than the value set to the 'hostname' option.

CLI: --hostname-admin

Env: KC_HOSTNAME_ADMIN

hostname-admin-url

Set the base URL for accessing the administration console, including scheme, host, port and path

CLI: --hostname-admin-url

Env: KC_HOSTNAME_ADMIN_URL

hostname-path

This should be set if proxy uses a different context-path for Keycloak.

CLI: --hostname-path

Env: KC_HOSTNAME_PATH

hostname-port

The port used by the proxy when exposing the hostname.

Set this option if the proxy uses a port other than the default HTTP and HTTPS ports.

CLI: --hostname-port

Env: KC_HOSTNAME_PORT

-1

hostname-strict

Disables dynamically resolving the hostname from request headers.

Should always be set to true in production, unless proxy verifies the Host header.

CLI: --hostname-strict

Env: KC_HOSTNAME_STRICT

true, false

true

hostname-strict-backchannel

By default backchannel URLs are dynamically resolved from request headers to allow internal and external applications.

If all applications use the public URL this option should be enabled.

CLI: --hostname-strict-backchannel

Env: KC_HOSTNAME_STRICT_BACKCHANNEL

true, false

false

hostname-url

Set the base URL for frontend URLs, including scheme, host, port and path.

CLI: --hostname-url

Env: KC_HOSTNAME_URL

proxy

The proxy address forwarding mode if the server is behind a reverse proxy.

CLI: --proxy

Env: KC_PROXY

none, edge, reencrypt, passthrough

none

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