# Device Shadow error messages
<a name="device-shadow-error-messages"></a>

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) |  +  Invalid JSON <br />+  Missing required node: state <br />+  State node must be an object <br />+  Desired node must be an object <br />+  Reported node must be an object <br />+  Invalid version <br />+  Invalid clientToken  A client token that is longer than 64 bytes will cause this response.  <br />+  JSON contains too many levels of nesting; maximum is 6 <br />+  State contains an invalid node   | 
| 401 (Unauthorized) |  +  Unauthorized   | 
| 403 (Forbidden) |  +  Forbidden   | 
| 404 (Not Found) |  +  Thing not found <br />+  No shadow exists with name: {{shadowName}}   | 
| 409 (Conflict) |  +  Version conflict   | 
| 413 (Payload Too Large) |  +  The payload exceeds the maximum size allowed   | 
| 415 (Unsupported Media Type) |  +  Unsupported documented encoding; supported encoding is UTF-8   | 
| 429 (Too Many Requests) |  +  The Device Shadow service will generate this error message when there are more than 10 in-flight requests on a single connection. An in-flight request is an in-progress request that has been started but not yet completed.   | 
| 500 (Internal Server Error) |  +  Internal service failure   |