Amazon Forecast is no longer available to new customers. Existing customers of Amazon Forecast can continue to use the service as normal. [Learn more"](https://aws.amazon.com/blogs/machine-learning/transition-your-amazon-forecast-usage-to-amazon-sagemaker-canvas/)

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

The optional metadata that you apply to a resource to help you categorize and organize them. Each tag consists of a key and an optional value, both of which you define.

The following basic restrictions apply to tags:
+ Maximum number of tags per resource - 50.
+ For each resource, each tag key must be unique, and each tag key can have only one value.
+ Maximum key length - 128 Unicode characters in UTF-8.
+ Maximum value length - 256 Unicode characters in UTF-8.
+ If your tagging schema is used across multiple services and resources, remember that other services may have restrictions on allowed characters. Generally allowed characters are: letters, numbers, and spaces representable in UTF-8, and the following characters: \$1 - = . \$1 : / @.
+ Tag keys and values are case sensitive.
+ Do not use `aws:`, `AWS:`, or any upper or lowercase combination of such as a prefix for keys as it is reserved for AWS use. You cannot edit or delete tag keys with this prefix. Values can have this prefix. If a tag value has `aws` as its prefix but the key does not, then Forecast considers it to be a user tag and will count against the limit of 50 tags. Tags with only the key prefix of `aws` do not count against your tags per resource limit.

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

 ** Key **   <a name="forecast-Type-Tag-Key"></a>
One part of a key-value pair that makes up a tag. A `key` is a general label that acts like a category for more specific tag values.  
Type: String  
Length Constraints: Minimum length of 1. Maximum length of 128.  
Pattern: `^([\p{L}\p{Z}\p{N}_.:/=+\-@]*)$`   
Required: Yes

 ** Value **   <a name="forecast-Type-Tag-Value"></a>
The optional part of a key-value pair that makes up a tag. A `value` acts as a descriptor within a tag category (key).  
Type: String  
Length Constraints: Minimum length of 0. Maximum length of 256.  
Pattern: `^([\p{L}\p{Z}\p{N}_.:/=+\-@]*)$`   
Required: Yes

## See Also
<a name="API_Tag_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/forecast-2018-06-26/Tag) 
+  [AWS SDK for Java V2](https://docs.aws.amazon.com/goto/SdkForJavaV2/forecast-2018-06-26/Tag) 
+  [AWS SDK for Ruby V3](https://docs.aws.amazon.com/goto/SdkForRubyV3/forecast-2018-06-26/Tag)