# Restrictions for tags on AWS Elemental MediaConvert resources
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The following basic restrictions apply to tags:
+ Maximum number of tags per resource – 50.
+ Maximum **Key** length – 128 Unicode characters.
+ Maximum **Value** length – 256 Unicode characters.
+ Valid values for **Key** and **Value** – Uppercase and lowercase letters in the UTF-8 character set, numbers, space, and the following characters: \$1 . : / = \$1 - and @.
+ Tag keys and values are case sensitive.
+ Don't use the `aws:` prefix for either keys or values. It's reserved for AWS use.