# Missing environment variable

Learn how to set up the required environment variables.

If you see an error like the one below, one of the required environment variables is not set:

> **Error**
>
> Did you forget to set the `PUBLIC_CROCT_APP_ID` environment variable?

See the [environment variables reference](/reference/sdk/hydrogen/api/environment-variables) for the full list, and the [setup section](/reference/sdk/hydrogen/manual-installation#environment-variables) for instructions on how to set them.