Variables

Variables provide a powerful way to manage configuration and secrets across services in Railway.

How it Works

When defined, variables are made available to your application as environment variables in the following scenarios:

• The build process for each service deployment.
• The running service deployment.
• The command invoked by railway run <COMMAND>
• The local shell via railway shell

In Railway, there is also a notion of configuration variables which allow you to control the behavior of the platform.

Template Syntax

Railway's templating syntax gives you flexibility in managing variables:

${{NAMESPACE.VAR}}

• NAMESPACE - The value for NAMESPACE is determined by the location of the variable being referenced. For a shared variable, the namespace is "shared". For a variable defined in another service, the namespace is the name of the service, e.g. "Postgres" or "backend-api".
• VAR - The value for VAR is the name, or key, of the variable being referenced.

You can also combine additional text or even other variables, to construct the values that you need:

DOMAIN=${{shared.DOMAIN}}
GRAPHQL_PATH=/v1/gql
GRAPHQL_ENDPOINT=https://${{DOMAIN}}/${{GRAPHQL_PATH}}

Types of Variables

In Railway, there is a notion of service variables, shared variables, reference variables, sealed variables, and a few kinds of reserved variables.

Service Variables

Service variables are scoped to a specific service. They can be referenced in other services by using a Reference Variable.

Shared Variables

Shared variables are scoped to a project and environment. They help reduce duplication of variables across multiple services within the same project.

Reference Variables

Reference variables are those defined by referencing variables in other services, shared variables, or even variables in the same service. This is useful for ease of maintenance, allowing you to set a variable in a single place and reference it as needed.

Reference variables use Railway's template syntax.

Sealed Variables

Sealed variables are scoped to a specific service. Once a variable is sealed, its value is not visible via the UI or the Railway API.

Variable Functions

Template variable functions allow you to dynamically generate variables (or parts of a variable) on demand when the template is deployed.

Railway-Provided Variables

Railway provides the following additional system environment variables to all builds and deployments.

Git Variables

These variables are provided if the deploy originated from a GitHub trigger.

User-Provided Configuration Variables

Users can use the following environment variables to configure Railway's behavior.

Support

For information on how to use variables refer to the Variables guide.