# UserProperty
<a name="API_UserProperty"></a>

A key-value pair that you define in the header. Both the key and the value are either literal strings or valid [substitution templates](https://docs.aws.amazon.com/iot/latest/developerguide/iot-substitution-templates.html).

## Contents
<a name="API_UserProperty_Contents"></a>

 ** key **   <a name="iot-Type-UserProperty-key"></a>
A key to be specified in `UserProperty`.  
Type: String  
Length Constraints: Minimum length of 0. Maximum length of 1024.  
Required: Yes

 ** value **   <a name="iot-Type-UserProperty-value"></a>
A value to be specified in `UserProperty`.  
Type: String  
Length Constraints: Minimum length of 0. Maximum length of 1024.  
Required: Yes

## See Also
<a name="API_UserProperty_SeeAlso"></a>

For more information about using this API in one of the language-specific AWS SDKs, see the following:
+  [AWS SDK for C\$1\$1](https://docs.aws.amazon.com/goto/SdkForCpp/iot-2015-05-28/UserProperty) 
+  [AWS SDK for Java V2](https://docs.aws.amazon.com/goto/SdkForJavaV2/iot-2015-05-28/UserProperty) 
+  [AWS SDK for Ruby V3](https://docs.aws.amazon.com/goto/SdkForRubyV3/iot-2015-05-28/UserProperty)