# Access Control
Access control pertains to controlling permissions for publish (PUBLISH) and subscribe (SUBSCRIBE) operations, which can be implemented at three levels:
- Client ID
- All users: controls permissions for topics without distinguishing between client ID and username.
Access control uses a blacklist mode by default. Also, the combination of clientid/username + topic is unique, which means that only the latest record for the same clientid/username + topic is considered valid.
# View Access Control Policy
Click Authentication & ACL -> ACL on the left navigation menu. You can switch between the three levels to view corresponding access control policy.
# Add Access Control Policy
For example to add an access control policy for certain clients, you can follow the steps below:
On the Client ID tab, click + Add, fill in the Client ID, Topic, select the action for this target user (Publish, Subscribe, or Publish & Subscribe), then add Permission (Allow or Deny), and then click Confirm to complete the addition.
Placeholders like %u (username) and %c (client ID) are allowed in the topic, and EMQX Cloud will automatically fill in the client information when a request is made.
The above steps also apply to the Username and All Users tab.
# Delete Access Control Policy
To delete access control information, simply click the delete icon on the right-hand side of the access control policy.