# Errors
Optimized.App employs standard HTTP response codes to signify the outcome of an API request. Typically, codes within the 2xx range signify a successful operation. Codes within the 4xx range point to an error coming from the provided information (for example, missing a necessary parameter or having invalid data). Codes in the 5xx range are indicative of issues with Optimized.App servers, though these occurrences are uncommon.
| HTTP status code | Description |
|  --- | --- |
| 200 | Request was made successfully. |
| 201 | Request was made successfully and a resource was created. |
| 204 | Request was made successfully and no content was returned. |
| 400 | The request was rejected, often due to missing a required parameter. |
| 401 | API token is not valid. |
| 403 | API token has no permission to perform the request. |
| 404 | The requested resource does not exist. |
| 405 | The request method is not allowed for the resource. |
| 422 | The request was rejected, often due to invalid client data. |
| 429 | Too many requests hit the API too quickly. We advise implementing an exponential backoff strategy for your requests. |
| 500 | Something went wrong on our end. |
| 503 | An unexpected spike in API access traffic. The server is usually operational within a short period of time. If the outage persists or you receive any other form of an HTTP 5XX error, please contact support. |