# Metadata

> Information about the app and the environment it's running in

Encore tries to give your code the same environment wherever it runs, but sometimes it helps to know more: which environment you're in, which cloud it runs on, or where the app can be reached. The `encore.env` module provides this information.

## Application metadata

Call `app_meta()` to get an `AppMeta` object describing the running application. It's also available as `encore.app_meta()`.

```python
from encore import env

meta = env.app_meta()
print(meta.app_id, meta.environment.name, meta.environment.type)
```

The metadata is read on first use, and every later call returns the same object. All the metadata classes are frozen dataclasses.

`AppMeta` has these attributes:

| Attribute | Description |
| --- | --- |
| `app_id` | The Encore application ID. Empty if the app isn't linked to Encore Cloud. |
| `app_slug` | The application's human-readable slug, as shown in the Encore Cloud dashboard and used by the CLI. Empty if the app isn't linked. Unlike `app_id`, it can change if the app is renamed. Locally the two are the same. |
| `gateways` | The API gateways serving the app, as a `dict` of gateway name to `GatewayMeta`. |
| `environment` | The [environment](/docs/platform/deploy/environments) the app is running in, as `EnvironmentMeta`. |
| `build` | The build the running code came from, as `BuildMeta`. |
| `deploy` | This deployment, as `DeployMeta`. |

### Environment

`meta.environment` is an `EnvironmentMeta` with:

- `name`: the environment's name. For local development it's `"local"`.
- `type`: one of `"production"`, `"development"`, `"ephemeral"` or `"test"`. It's `"development"` under `encore run` and `"test"` under `encore test`.
- `cloud`: one of `"aws"`, `"gcp"`, `"azure"`, `"encore"` or `"local"`. It's `"local"` for local development.

### Gateways

An app can have several API gateways, so there's no single base URL for its API. Look up the gateway you need by name:

```python
gw = env.app_meta().gateways.get("api")
if gw is not None:
    print("api is at", gw.base_url)
```

Each `GatewayMeta` has a `name` and a `base_url`. Locally, `base_url` is `http://localhost:<port>`, typically `http://localhost:4000`. If the environment uses a custom domain, `base_url` uses it, but note that it reflects the domain at the time of deployment. A process that serves no gateway, such as a worker, gets an empty `dict`.

To call another service directly rather than through a gateway, use [`encore.services.base_url`](/docs/py/primitives/services).

### Build and deployment

- `build.revision`: the version control revision the app was built from.
- `deploy.id`: the deployment's unique ID, generated by Encore Cloud.
- `deploy.time`: when this build was deployed to the environment, as a timezone-aware `datetime`.
- `deploy.hosted_services`: the services this deployment hosts, as a list of `HostedService`, each with a `name`.

## Example use cases

### Behaving differently by environment

Use the environment type rather than its name when behavior should follow the kind of environment, so it keeps working as you add environments:

```python
from encore import env


def send_email(to: str, subject: str, body: str) -> None:
    if env.app_meta().environment.type != "production":
        print(f"email to {to}: {subject}")  # don't email real users outside production
        return
    # ... send it for real
```

### Using cloud-specific services

Encore supports a common set of infrastructure on every cloud. For services it doesn't cover, branch on the cloud the environment runs on. For example, to write audit logs to a data warehouse:

```python
from encore import env


async def write_audit_log(entry: dict) -> None:
    cloud = env.app_meta().environment.cloud
    if cloud == "gcp":
        await write_to_bigquery(entry)
    elif cloud == "aws":
        await write_to_redshift(entry)
    else:
        write_to_file(entry)
```

For values that differ between environments, prefer [configuration](/docs/py/develop/config) over checking the environment in code.