# Problems

This reference lists the custom [problem types](https://docs.devland.is/technical-overview/api-design-guide/errors) that our APIs use.

## Standard http problems

* [400 Bad Request](https://httpstatuses.io/400)
* [401 Unauthorized](https://httpstatuses.io/401)
* [403 Forbidden](https://httpstatuses.io/403)
* [404 Not Found](https://httpstatuses.io/404)
* [500 Internal Server Error](https://httpstatuses.io/500)

## Custom problems

* [400 Validation Failed](https://docs.devland.is/reference/problems/validation-failed)
* [403 Bad Subject](https://docs.devland.is/reference/problems/bad-subject)