# Environment variable

A process-level name and value used to pass configuration, endpoints, and connection information to an application.

Also known as: environment configuration, env var

Aspire supplies environment variables to running resources for configuration such as:

- `ConnectionStrings__resourcename` for a named connection string.
- `services__servicename__https__0` for a service's HTTPS endpoint.
- Custom settings configured with `WithEnvironment` in C# or `withEnvironment` in TypeScript.

Applications read these through their runtime's environment APIs or a configuration library. .NET configuration maps double underscores to configuration separators; JavaScript and Python can read the original environment variable names directly.

Values can contain secrets. Avoid copying sensitive environment values into bug reports or sharing them publicly.

## Practical example

Inspect a service's environment in the dashboard to see which connection strings and endpoint settings the AppHost supplied.

## Learn more

- [Configure environment variables for your resources](https://aspire.dev/fundamentals/environment-variables/)

## Related terms

- [Connection string](https://aspire.dev/hub/glossary/connection-string/)

- [Polyglot](https://aspire.dev/hub/glossary/polyglot/)

- [Service discovery](https://aspire.dev/hub/glossary/service-discovery/)