# Connections

Connections are used to connect to external systems. For example, they are used to read and write data from databases, files, and other systems when running replications.

![Sling Platform Connections](https://3453272330-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M93cpHl7B7NPZlDrubS%2Fuploads%2Fgit-blob-10858a01ad4753ab62e560b6c686e48e424b560e%2Fsling-platform-connections.png?alt=media)

## Project env.yaml vs Agent env.yaml

Each project has an internal `env.yaml` file, which is used to store the connection credentials. This file is used to authenticate the agent when it needs to access the external system. When using the project env.yaml file, the credentials are securely transmitted over TLS and encrypted at rest.

You can also define a local `env.yaml` file (saved on the agent machine), which can be used to authenticate the agent when it needs to access the external system. When using the local env.yaml file, the credentials are never transmitted outside the agent machine. Only the name and type of the connection are sent to the control server for displaying on the UI.

### Project env.yaml

To add a connection to the project env.yaml file, you can click on the `New` button on the connections page and then select the type of connection you want to add.

![Sling Platform Connections New](https://3453272330-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M93cpHl7B7NPZlDrubS%2Fuploads%2Fgit-blob-bd298bc45fab3edf1ca872b05e82301a6b1d80de%2Fsling-platform-connections-new.png?alt=media)

You can then fill in the connection details and click on the `Save` button to add the connection to the project env.yaml file. You can also click on the `Test` button to test the connection before saving it.

![Sling Platform Connections Save](https://3453272330-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M93cpHl7B7NPZlDrubS%2Fuploads%2Fgit-blob-4eb94e4d9d348b11b26fbd09d8270295947cda19%2Fsling-platform-connections-save.png?alt=media)

## Explore Connections

You can explore the files or tables in a connection by clicking one on the left sidebar. This allows you to see which objects are available, as well as previewing the data inside. This is useful for getting familiar with the data, and for finding the correct object names for your replications.&#x20;

![Sling Platform Connections Explore](https://3453272330-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M93cpHl7B7NPZlDrubS%2Fuploads%2Fgit-blob-61828ec7b0893808c91216e3fc857bec3cd34329%2Fsling-platform-connections-explore.png?alt=media)

{% hint style="warning" %}
Note that objects are accessed in a read-only fashion, therefore no changes can be made to the data.
{% endhint %}
