# Deploy a version to an environment

Deploying a version makes an environment serve it. You deploy from the **Deployments** dialog, where you also add environments and choose the release target. Every change in the dialog is staged until you select **Apply changes**.

## Before you begin

- The agent has at least one published version. See [Publish a version](https://docs.faustine.ai/web-agents/publish-a-version/).
- Every variable the version uses has a default or a value on the environment you deploy to.

## Deploy a version

To change the version an environment serves:

1. In the portal, go to [**Web Agents**](https://auth.faustine.ai/go?to=%2Fweb-assistants) and select your agent.
2. In the agent's header, select the control that lists each environment with the version it serves. The **Deployments** dialog opens.
3. Under the environment, select the version. Versions are listed from oldest to newest, and the one the environment serves is marked **Live**.
4. Select **Yes, serve** with the version number to confirm.
5. Select **Apply changes**.

The header shows the new version next to the environment. Pages of that environment get it on their next load.

## Add an environment

To add an environment such as Staging:

1. In the **Deployments** dialog, select **Add environment**.
2. Enter a name and select **Add**. The new environment is set to serve the latest version. To serve another one, select it.
3. Select **Apply changes**.

To load the environment from your app, pass its name in the install snippet: `env: 'Staging'` in `Faustine.init`, or `&env=Staging` on the script URL. A new environment has no allowed domains and its own variable values, which start empty and fall back to each variable's default.

## Change the release target

The release target is the environment that serves every new version as soon as you publish it. To publish to Staging first and deploy to Production yourself, make Staging the release target.

To change it:

1. In the **Deployments** dialog, under **Release target**, select the environment.
2. Select **Yes, use** with the environment's name to confirm.
3. Select **Apply changes**.

The next publish is served on the new release target. The previous one keeps the version it serves.

## Deploy the latest version to the release target

When the release target does not serve the latest version, the agent's header says which version it still serves and shows a **Deploy** button with the version and the environment, for example **Deploy v5 to Staging**. Select it to serve the latest version there without opening the dialog.

## Remove an environment

In the **Deployments** dialog, select the remove control of the environment, then **Apply changes**. The release target cannot be removed, and an agent keeps at least one environment.

A page that names the removed environment stops loading the agent. Change the install snippet of every site that loads an environment before you remove it.

## Troubleshooting

| Symptom | Cause | Fix |
| --- | --- | --- |
| The dialog shows `No published versions yet` | The agent has no version. | [Publish a version](https://docs.faustine.ai/web-agents/publish-a-version/) first. |
| **Apply changes** is not available and the dialog says `Confirm or dismiss the highlighted change first.` | A version or a release target is selected and not confirmed. | Confirm it, or keep the current one. |
| Applying fails for one environment | A variable of the version has no default and no value on that environment. | Set the value in the **Variables** tab, then apply again. |
| `An environment with that name already exists.` | Environment names are unique within an agent, ignoring letter case. | Enter another name. |

## Next steps

- [Roll back to an earlier version](https://docs.faustine.ai/web-agents/roll-back/): serve the previous version on an environment.
- [Set variables for each environment](https://docs.faustine.ai/web-agents/variables/): give the new environment its values.
- [Restrict the domains that can load the agent](https://docs.faustine.ai/web-agents/restrict-domains/): set the allowed domains of the environment.
- [Versions, environments and deployments](https://docs.faustine.ai/web-agents/versions-and-environments/): how publishing and deploying relate.