EC2 > Structures > Tag Tag¶ Structure Class¶ Tag dataclass ¶ Bases: _SerdeShape Describes a tag. Attributes¶ key class-attribute instance-attribute ¶ key: str | None = ... The key of the tag. Constraints: Tag keys are case-sensitive and accept a maximum of 127 Unicode characters. May not begin with aws:. value class-attribute instance-attribute ¶ value: str | None = ... The value of the tag. Constraints: Tag values are case-sensitive and accept a maximum of 256 Unicode characters.