A human-readable string describing any system errors encountered by this UnityWebRequest object while handling HTTP requests or responses. (Read Only)
If the UnityWebRequest has not encountered a system error, this property will return null. Examples of system errors include socket errors, errors resolving DNS entries, or the redirect limit being exceeded.
Note: Error-type return codes from the server, such as 404/File Not Found or 500/Internal Server Error are not considered system errors.
Default value: null.
Additional resources: responseCode.