# Writing your own OAuthenticator

There are two ways to write your own OAuthenticator.

## Using GenericOAuthenticator

```{note}
Before writing your own config, [](tutorials:provider-specific:generic) may already have an example for your service.
```

The first and simplest is to use the `oauthenticator.generic.GenericOAuthenticator` class
and configuration to set the necessary configuration variables.

- client_id
- client_secret
- login_service
- userdata_url
- token_url
- username_claim

Example config:

```python
c.JupyterHub.authenticator_class = "generic-oauth"

c.GenericOAuthenticator.oauth_callback_url = 'https://{host}/hub/oauth_callback'
c.GenericOAuthenticator.client_id = 'OAUTH-CLIENT-ID'
c.GenericOAuthenticator.client_secret = 'OAUTH-CLIENT-SECRET-KEY'
c.GenericOAuthenticator.login_service = 'name-of-service-provider'
c.GenericOAuthenticator.userdata_url = 'url-retrieving-user-data-with-access-token'
c.GenericOAuthenticator.token_url = 'url-retrieving-access-token-oauth-completion'
c.GenericOAuthenticator.username_claim = 'username-key-for-USERDATA-URL'
```

## Writing your own OAuthenticator class

If you want more advanced features and customization beyond the basics of OAuth,
you can write your own full OAuthenticator subclass,
which enables more detailed customization login and logout actions.

The skeleton of an OAuthenticator looks like this:

```{literalinclude} example-oauthenticator.py

```

where you will need to find and define the URLs and requests necessary to complete OAuth with your provider.

````{note}
For a visual of the requests and information exchanged during the JupyterHub's external OAuthentication process,
checkout the diagram below and also the [JupyterHub docs](https://jupyterhub.readthedocs.io/en/stable/reference/oauth.html).

```{image} /_static/images/JupyterHub-OAuth-external-flow.png
```
````