Badges are subtle status and notification indicators. They're read-only and not interactive.
Usage
When to use
We have 2 types of badges, the number badge and dot badge. The number badge is commonly used to indicate the number of outstanding notifications. The dot badge is used to indicate that the status has changed or attention is needed.
How best to use
Don't
Don't customise the colour of the dot badge.
Don't
Don't allow users to interact with the badge, as it's a status indication only.
When not to use
Don't use it with important or urgent statuses
Use page-level messages or other ways to communicate important information upfront, as badges are for subtle notifications only.