Environment Variables

Last updated Sep 29, 2026

Runtime environment variables

The container runtime automatically sets the following variables:

• CLOUDFLARE_APPLICATION_ID - the ID of the Containers application
• CLOUDFLARE_COUNTRY_A2 - the ISO 3166-1 Alpha 2 code ↗︎ of a country the container is placed in
• CLOUDFLARE_LOCATION - a name of a location the container is placed in
• CLOUDFLARE_REGION - a region name
• CLOUDFLARE_DURABLE_OBJECT_ID - the ID of the Durable Object instance that the container is bound to. You can use this to identify particular container instances on the dashboard.

User-defined environment variables

You can set environment variables when defining a Container in your Worker, or when starting a container instance.

For example:

class MyContainer extends Container {
    defaultPort = 4000;
    envVars = {
        MY_CUSTOM_VAR: "value",
        ANOTHER_VAR: "another_value",
    };
}

More details about defining environment variables and secrets can be found in this example.

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