# Tag
<a name="API_Tag"></a>

A key-value pair. A tag consists of a tag key and a tag value. Tag keys and tag values are both required, but tag values can be empty (null) strings.

**Important**  
Do not include confidential or sensitive information in this field. This field may be displayed in plaintext in CloudTrail logs and other output.

For information about the rules that apply to tag keys and tag values, see [User-Defined Tag Restrictions](https://docs.amazonaws.cn/awsaccountbilling/latest/aboutv2/allocation-tag-restrictions.html) in the * Amazon Billing and Cost Management User Guide*.

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

**Note**  
In the following list, the required parameters are described first.

 ** TagKey **   <a name="KMS-Type-Tag-TagKey"></a>
The key of the tag.  
Type: String  
Length Constraints: Minimum length of 1. Maximum length of 128.  
Required: Yes

 ** TagValue **   <a name="KMS-Type-Tag-TagValue"></a>
The value of the tag.  
Type: String  
Length Constraints: Minimum length of 0. Maximum length of 256.  
Required: Yes

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

For more information about using this API in one of the language-specific Amazon SDKs, see the following:
+  [Amazon SDK for C\$1\$1](https://docs.amazonaws.cn/goto/SdkForCpp/kms-2014-11-01/Tag) 
+  [Amazon SDK for Java V2](https://docs.amazonaws.cn/goto/SdkForJavaV2/kms-2014-11-01/Tag) 
+  [Amazon SDK for Ruby V3](https://docs.amazonaws.cn/goto/SdkForRubyV3/kms-2014-11-01/Tag)