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To recognize that a user has logged out, you can use Ory's logout tokens and logout flows. When a user logs out, their session is terminated, and they are no longer able to access protected resources. Ory issues logout tokens with the

ory_lo_

prefix, which makes them easily identifiable and distinguishes them from other types of tokens ([source](https://www.ory.sh/docs/security-compliance/token-formats)). Ory provides logout on all supported clients, including server-rendered browser applications, single page applications (SPA), and native API applications. In each case, Ory first generates a logout URL for a given Ory Session cookie. You can then open the logout URL in the browser or call it using an AJAX request ([source](https://www.ory.sh/docs/kratos/self-service/flows/user-logout)). Here is an example of how to handle logout in a server-side application:

javascript import { Configuration, OAuth2Api } from "@ory/client"   import { Request, Response } from "express"      const ory = new OAuth2Api(    new Configuration({    basePath: `https://${process.env.ORY_PROJECT_SLUG}.<http://projects.oryapis.com|projects.oryapis.com>`,    accessToken: process.env.ORY_API_KEY,    }),   )      export async function handleLogout(request: Request, response: Response) {    const challenge = request.query.logout_challenge.toString()    const { data: logoutRequest } = await ory.getOAuth2LogoutRequest({    logoutChallenge: challenge.toString(),    })       // The user did not want to sign out from the given app.    if (!allowLogout()) {    await ory    .rejectOAuth2LogoutRequest({    logoutChallenge: challenge,    })    .then(() => {    // Do something - redirect somewhere, for example the default home page.    })    return    }       ory    .acceptOAuth2LogoutRequest({    logoutChallenge: challenge,    })    .then(({ data }) => response.redirect(data.redirect_to))   }

([source](https://www.ory.sh/docs/hydra/guides/logout)) In this example, the

handleLogout

function checks if the user wants to log out by calling

ory.getOAuth2LogoutRequest

. If the user does not want to log out, the function calls

ory.rejectOAuth2LogoutRequest

. If the user does want to log out, the function calls

ory.acceptOAuth2LogoutRequest

and then redirects the user to the specified URL. You can use this information to update your cache when a user logs out.

In a self-hosted Ory Kratos setup, you can recognize that a user has logged out by observing the deletion of the user's session cookie. When a user logs out, their session cookie is deleted, which effectively ends their session. To implement this, you can set up a middleware in your gateway that checks for the presence of the session cookie in each request. If the cookie is not present, this means that the user is not logged in or has logged out. Here's a simple example of how you might implement this in a Node.js Express application:

javascript app.use((req, res, next) => {   if (!req.cookies['ory_kratos_session']) {     console.log('User is not logged in or has logged out');     // Handle the logout event here, e.g. by clearing cached data   }   next(); });

In this example,

ory_kratos_session

is the name of the session cookie. You should replace this with the actual name of your session cookie. Please note that this is a simplified example and actual implementation may vary based on your application's requirements and the specifics of your setup. For more information on handling sessions in Ory Kratos, you can refer to the [Session Management Overview](https://www.ory.sh/docs/kratos/session-management/overview) in the Ory documentation.

Based on the provided extracts, Ory Kratos does not directly support webhooks for logout events. The extracts mention the use of webhooks for various events and actions, such as user registration, profile updates, and integration with third-party systems, but there's no specific mention of logout events. However, you can implement a custom solution to achieve this. For example, you could create a custom endpoint in your application that is called when a user logs out. This endpoint could then trigger a webhook to notify other parts of your system or external services. Here's a simplified example of how you might implement this in a Node.js Express application:

javascript <http://app.post|app.post>('/logout', (req, res) => {   // Handle the logout process here, e.g. by deleting the session cookie    // Trigger the webhook   <http://axios.post|axios.post>('<https://your-webhook-url>', {     event: 'user_logout',     user_id: req.user.id   });    res.redirect('/login'); });

In this example,

<https://your-webhook-url>

is the URL of your webhook. You should replace this with the actual URL of your webhook. Please note that this is a simplified example and actual implementation may vary based on your application's requirements and the specifics of your setup. For more information on using webhooks with Ory, you can refer to the [Ory Actions and webhooks documentation](https://www.ory.sh/docs/guides/integrate-with-ory-cloud-through-webhooks).