# Error Handling

Although Celltick servers have fail safe layers that would try to always return content, even in case of server errors, we cannot guarantee a valid response to always be received as the request or response might be blocked because of network conditions. It is strongly encouraged that the application would handle a case where no content is returned to the application within a reasonable time, or when an error response is received.

{% hint style="info" %}
If an invalid request is sent to the API, Celltick returns one of the following HTTP Status Codes.

* 400 Bad Request Invalid publisher, invalid URL path or missing required parameter or wrong named parameter&#x20;
* 401 Unauthorized partner name or Invalid API key&#x20;
* 429 Too Many Requests Rate limit exceeded Any 5xx type code An unintended server error has occurred
  {% endhint %}
