# API

Headscale provides a [HTTP REST API](#rest-api) which may be used to integrate a [web
interface](integration/web-ui.md), [remote control Headscale](#remote-control) or provide a base for custom
integration and tooling.

The API requires a valid API key before use. To create an API key, log into your Headscale server and generate
one with the default expiration of 90 days:

```shell
headscale apikeys create
```

Copy the output of the command and save it for later. Please note that you can not retrieve an API key again. If the API
key is lost, expire the old one, and create a new one.

To list the API keys currently associated with the server:

```shell
headscale apikeys list
```

and to expire an API key:

```shell
headscale apikeys expire --prefix <PREFIX>
```

## REST API

- API endpoint: `/api/v1`, e.g. `https://headscale.example.com/api/v1`
- Documentation: `/api/v1/docs`, e.g. `https://headscale.example.com/api/v1/docs`
- Headscale Version: `/version`, e.g. `https://headscale.example.com/version`
- Authenticate using HTTP Bearer authentication by sending the [API key](#api) with the HTTP `Authorization: Bearer <API_KEY>` header.

Start by [creating an API key](#api) and test it with the examples below. Read the API documentation provided by your
Headscale server at `/api/v1/docs` for details.

=== "Get details for all users"

    ```console
    curl -H "Authorization: Bearer <API_KEY>" \
        https://headscale.example.com/api/v1/user
    ```

=== "Get details for user 'bob'"

    ```console
    curl -H "Authorization: Bearer <API_KEY>" \
        https://headscale.example.com/api/v1/user?name=bob
    ```

=== "Register a node"

    ```console
    curl -H "Authorization: Bearer <API_KEY>" \
        --json '{"user": "<USER>", "authId": "<AUTH_ID>"}' \
        https://headscale.example.com/api/v1/auth/register
    ```

## Join nodes with an OAuth client

Headscale also serves a subset of the Tailscale-compatible API at `/api/v2`, which
accepts **OAuth 2.0 client-credentials** in addition to API keys. The Tailscale
client can use an OAuth client secret in place of an auth key: it exchanges the
secret for an access token, mints a single-use tagged auth key and registers with
it. This works anywhere the client takes an auth key: `tailscale up`, the
container image, `tsnet` and the
[`tailscale/github-action`](https://github.com/tailscale/github-action). One
long-lived secret joins any number of nodes.

Create an OAuth client with the `auth_keys` scope and the tags its nodes get. The
secret is shown once:

```shell
headscale oauth-clients create --scope auth_keys --tag tag:ci
```

Build the auth key from the secret:

1. Swap the prefix: `hskey-client-…` becomes `tskey-client-…`. The client only
   runs the exchange for `tskey-client-`; Headscale accepts both.
1. Append `?baseURL=<your Headscale URL>`.
1. Set `--advertise-tags`. Each tag must exist in the policy's `tagOwners` and be
   one of the OAuth client's tags, or owned by one of them.

```text
tskey-client-<id>-<secret>?baseURL=https://headscale.example.com
```

!!! warning

    Without `baseURL` the client sends the secret to `https://api.tailscale.com`.

### Attributes

These are all the attributes the client understands; any other is an error.
Order does not matter and an empty value means the default.

| Attribute       | Default                     | Effect                                                                                           |
| --------------- | --------------------------- | ------------------------------------------------------------------------------------------------ |
| `baseURL`       | `https://api.tailscale.com` | Where the exchange and key creation go. Your Headscale URL, no trailing slash.                   |
| `ephemeral`     | `true`                      | Node is removed after it goes offline (`node.ephemeral.inactivity_timeout`). `false` to keep it. |
| `preauthorized` | `false`                     | Accepted, no effect: Headscale always authorizes pre-auth-key nodes.                             |

Booleans take any Go `strconv.ParseBool` value (`true`, `false`, `1`, `0`, …).

### Examples

`tailscale up`, either as the auth key or via `--client-secret` (which also takes
`file:/path/to/secret`):

```shell
tailscale up --login-server https://headscale.example.com --advertise-tags tag:ci \
  --auth-key 'tskey-client-<id>-<secret>?baseURL=https://headscale.example.com&ephemeral=false'
```

Container image:

```shell
docker run -d --name tailscale \
  -e TS_AUTHKEY='tskey-client-<id>-<secret>?baseURL=https://headscale.example.com' \
  -e TS_EXTRA_ARGS='--login-server=https://headscale.example.com --advertise-tags=tag:ci' \
  tailscale/tailscale
```

`tsnet` (`TS_CLIENT_SECRET` works too); import `tailscale.com/feature/oauthkey`:

```go
srv := &tsnet.Server{
    ControlURL:    "https://headscale.example.com",
    AuthKey:       "tskey-client-<id>-<secret>?baseURL=https://headscale.example.com",
    AdvertiseTags: []string{"tag:ci"},
}
```

GitHub Action, with the whole string stored as a repository secret:

{% raw %}

```yaml
- uses: tailscale/github-action@v4
  with:
    authkey: ${{ secrets.HEADSCALE_AUTHKEY }}
    args: --login-server=https://headscale.example.com --advertise-tags=tag:ci
```

{% endraw %}

Use `authkey` even though upstream marks it deprecated: `oauth-secret` appends its
own `?…` to the secret, which corrupts `baseURL`.

## Remote control

The `headscale` binary can control a Headscale instance from a remote machine over the HTTP API.

### Prerequisite

- A workstation to run `headscale` (any supported platform, e.g. Linux).
- The Headscale server reachable over HTTP(S).
- An [API key](#api) to authenticate with the Headscale server.

### Setup remote control

1. Download the [`headscale` binary from GitHub's release page](https://github.com/juanfont/headscale/releases). Make
   sure to use the same version as on the server.

1. Put the binary somewhere in your `PATH`, e.g. `/usr/local/bin/headscale`

1. Make `headscale` executable: `chmod +x /usr/local/bin/headscale`

1. [Create an API key](#api) on the Headscale server.

1. Provide the connection parameters for the remote Headscale server either via a minimal YAML configuration file or
   via environment variables:

    === "Minimal YAML configuration file"

        ```yaml title="config.yaml"
        cli:
            address: <HEADSCALE_URL>
            api_key: <API_KEY>
        ```

    === "Environment variables"

        ```shell
        export HEADSCALE_CLI_ADDRESS="<HEADSCALE_URL>"
        export HEADSCALE_CLI_API_KEY="<API_KEY>"
        ```

    This instructs the `headscale` binary to connect to a remote instance at `<HEADSCALE_URL>` (e.g.
    `https://headscale.example.com`), instead of connecting to the local instance. A bare host without a scheme is
    assumed to be `https`.

1. Test the connection by listing all nodes:

    ```shell
    headscale nodes list
    ```

    You should now be able to see a list of your nodes from your workstation, and you can
    now control the Headscale server from your workstation.

### Behind a proxy

The remote CLI uses the same HTTP API as everything else, so it works through the reverse proxy already in front of
Headscale with no extra setup.

### Troubleshooting

- Make sure you have the _same_ Headscale version on your server and workstation.
- Verify that your TLS certificate is valid and trusted.
- If you don't have access to a trusted certificate (e.g. from Let's Encrypt), either:
    - Add your self-signed certificate to the trust store of your OS _or_
    - Disable certificate verification by either setting `cli.insecure: true` in the configuration file or by setting
      `HEADSCALE_CLI_INSECURE=1` via an environment variable. We do **not** recommend to disable certificate validation.