To logout using REST in Drupal 8, you can just do a **POST** with `Content-type: application/json` to:

 `https://example.com/user/logout?_format=json` 

## Earlier versions of Drupal 8

Do a **GET** on `?q=user/logout`

This is noted in the JS D8 REST docs: https://www.drupal.org/docs/8/core/modules/rest/javascript-and-drupal-8-restful-web-services

Although it should not matter, the `Content-type` may need to be set to `application/x-www-form-urlencoded`.

Here's an example usage from jDrupal: https://github.com/signalpoint/jDrupal/blob/8.x-1.x/src/includes/rest.inc.js#L113