> For the complete documentation index, see [llms.txt](https://docs.console.zenlayer.com/welcome/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.console.zenlayer.com/welcome/cn/content-delivery-network/domain-management/access-control/ua-restrictions.md).
# UA 限制
Zenlayer 内容分发网络允许您配置一个 User-Agent 黑名单来识别和过滤请求。通过这种方式，您可以限制对 CDN 资源的访问，提高服务安全性。
User-Agent 是一个 HTTP 头。它包含发出请求的客户端信息，包括操作系统（OS）、操作系统版本、浏览器和浏览器版本。
User-Agent 黑名单：User-Agent 头的值在黑名单中的请求将被拒绝。向客户端返回 HTTP 403 状态码。
### 黑名单
预期结果：UA 中的上述字段将被封堵。
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# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:
```
GET https://docs.console.zenlayer.com/welcome/cn/content-delivery-network/domain-management/access-control/ua-restrictions.md?ask=&goal=
```
`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.