When creating an EC2 instance in AWS, the instance name is set as the value of the Name tag. The tag key (Name) and tag value must follow certain conventions.

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

Allowed characters

Although EC2 allows for any character in its tags, other AWS services are more restrictive. The allowed characters across all AWS services are: letters (a-z, A-Z), numbers (0-9), and spaces representable in UTF-8, and the following characters: + - = . _ : / @.

If you enable instance tags in instance metadata, instance tag keys can only use letters (a-z, A-Z), numbers (0-9), and the following characters: + - = . , _ : @. Instance tag keys can't contain spaces or /, and can't comprise only . (one period), .. (two periods), or _index. For more information, see Work with instance tags in instance metadata.

Tag keys and values are case-sensitive.

The aws: prefix is reserved for AWS use. If a tag has a tag key with this prefix, then you can't edit or delete the tag's key or value. Tags with the aws: prefix do not count against your tags per resource limit.