Feature Overview

User-Agent is an HTTP request header. It contains the information that identifies the client making the request, including the OS, OS version, browser type, and browser version. The User-Agent header indicates the identity of a visitor and the tools used by the visitor. By identifying information included in the User-Agent header of an HTTP request, CDN can limit user behaviors and deny or allow access from users of a specific type, thus achieving hotlink protection, attack prevention, and the prevention of malicious access from stolen IP addresses.

• User-Agent trustlist: a list of access tools that users are allowed to use. A CDN point of presence (POP) denies access requests whose User-Agent header has a value not included in the User-Agent trustlist and returns the 403 status code. A CDN POP only allows access requests whose User-Agent header has a value in the User-Agent trustlist.

• User-Agent blocklist: a list of access tools that users are forbidden to use. A CDN POP only allows access requests whose User-Agent header has a value not included in the User-Agent blocklist. A CDN POP denies access requests whose User-Agent header has a value in the User-Agent blocklist and returns the 403 status code.

Additional Considerations

A User-Agent trustlist and a User-Agent blocklist cannot be configured at the same time. They are mutually exclusive.
If the value of the User-Agent field in a user request hits a value in the User-Agent blocklist, the request can still be sent to a CDN POP. However, the CDN POP denies the request and returns the 403 status code.

Procedure

Log in to the CDN console.
Go to Domain Management -> Domain List page.
On the Domain List page, find the target domain name, and click Edit in the Actions column.
Click Access Control .
Click User-Agent Trustlist/Blocklist tab.
Turn on switch. Off by default.
Select type, you can choose either trustlist or blocklist and then input the tartget UA, regex is supported.
Click Save and submit.

Examples

Case 1: UA blacklist

Parameter	example
UA switch	ON
Type	Blocklist: .Chrome.

Descriptions: When client UA contains keyword "Chrome", the request sent by the client will be refused and get 403 response.

Case 2: UA whitelist

Parameter	example
UA switch	ON
Type	Trustlist: .Firefox.

Descriptions: Only when client UA contains keyword "Firefox", the request from client will be allowed.

Content Delivery Network

UA blacklist/whitelist