# Device Shadow error messages The Device Shadow service publishes a message on the error topic (over MQTT) when an attempt to change the state document fails. This message is only emitted as a response to a publish request on one of the reserved `$aws` topics. If the client updates the document using the REST API, then it receives the HTTP error code as part of its response, and no MQTT error messages are emitted. **** | HTTP error code | Error messages | | --- | --- | | 400 (Bad Request) | [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/iot/latest/developerguide/device-shadow-error-messages.html) | | 401 (Unauthorized) | [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/iot/latest/developerguide/device-shadow-error-messages.html) | | 403 (Forbidden) | [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/iot/latest/developerguide/device-shadow-error-messages.html) | | 404 (Not Found) | [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/iot/latest/developerguide/device-shadow-error-messages.html) | | 409 (Conflict) | [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/iot/latest/developerguide/device-shadow-error-messages.html) | | 413 (Payload Too Large) | [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/iot/latest/developerguide/device-shadow-error-messages.html) | | 415 (Unsupported Media Type) | [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/iot/latest/developerguide/device-shadow-error-messages.html) | | 429 (Too Many Requests) | [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/iot/latest/developerguide/device-shadow-error-messages.html) | | 500 (Internal Server Error) | [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/iot/latest/developerguide/device-shadow-error-messages.html) |