# Restrictions that apply to tagging resources in Amazon EMR
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The following basic restrictions apply to tags:
+ Restrictions that apply to Amazon EC2 resources apply to Amazon EMR as well. For more information, see [https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/Using_Tags.html#tag-restrictions](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/Using_Tags.html#tag-restrictions).
+ Do not use the `aws:` prefix in tag names and values because it is reserved for AWS use. In addition, you cannot edit or delete tag names or values with this prefix.
+ You cannot change or edit tags on a terminated cluster.
+ A tag value can be an empty string, but not null. In addition, a tag key cannot be an empty string.
+ Keys and values can contain any alphabetic character in any language, any numeric character, white spaces, invisible separators, and the following symbols: \$1 . : / = \$1 - @ 

For more information about tagging using the AWS Management Console, see [Working with tags in the console](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/Using_Tags.html#Using_Tags_Console) in the *Amazon EC2 User Guide*. For more information about tagging using the Amazon EC2API or command line, see [API and CLI overview](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/Using_Tags.html#Using_Tags_CLI) in the *Amazon EC2 User Guide*.