# Tag Overview

Tags are used to identify and classify OBS buckets.

If you add tags to a bucket, charging data records (CDRs) generated by the requests for this bucket will be added with these tags, so that you can use the tags to classify CDRs for detailed cost analysis. For example, if a running application uploads data to a bucket, you can tag the bucket with the application name. In this manner, the costs on the application can be analyzed using tags on CDRs.

A tag is described using a key-value pair. A bucket can have a maximum of 20 tags. Each tag has only one key and one value.

The key and value can exist in either sequence in a tag. Each key is unique among all tags of a bucket, whereas values can be repetitive or blank.

Parent topic: Tags