请求头和响应头有什么区别？

请求头由客户端（浏览器或应用）发往服务器；响应头由服务器随答案返回。部分头如 Content-Type 两侧都可能出现。

HTTP 请求头名称区分大小写吗？

不区分。按规范名称大小写无关，Content-Type 与 content-type 含义相同。Title-Case 仅为约定写法。

Host 告知服务器请求指向哪个域名。HTTP/1.1 中必填，使一台服务器可按名称托管多个网站。

Cache-Control 规定响应可缓存多久；ETag 与 If-None-Match 让客户端询问“内容变了吗？”，未变则返回轻量的 304。

HTTP 请求头是每个请求与响应开头发送的键值对。它们携带内容类型、缓存规则、身份认证等元数据。本表帮你识别在构建或调试网络流量时最常见的请求头。

更新日期: 2026-09-10

请求头	方向	用途
Host	request	Identifies the server's host and port (from the URL).
User-Agent	request	Reports the client software (browser, OS, bot) making the request.
Accept	request	Lists the response media types (MIME) the client can handle.
Authorization	request	Carries credentials (token, Basic auth) to authenticate the client.
Content-Type	request/response	States the media type of the request or response body.
Content-Length	request/response	Gives the size in bytes of the request or response body.
Cookie	request	Sends stored key/value pairs from a previous response back to the server.
Set-Cookie	response	Server instructs the client to store a cookie for later requests.
Cache-Control	request/response	Directs caching behaviour: no-cache, max-age, private, etc.
ETag	response	Opaque identifier for a resource version, used for revalidation.
If-None-Match	request	Sends an ETag; server returns 304 if the resource is unchanged.
Location	response	Points the client to a new URL for redirects (3xx) or created resources.
Access-Control-Allow-Origin	response	Permits a browser to share a response across origins (CORS).
X-Forwarded-For	request	Records the client IP as seen through a proxy or load balancer.
Referer	request	Indicates the URL of the page that linked to the requested resource.

请求头和响应头有什么区别？: 请求头由客户端（浏览器或应用）发往服务器；响应头由服务器随答案返回。部分头如 Content-Type 两侧都可能出现。
HTTP 请求头名称区分大小写吗？: 不区分。按规范名称大小写无关，Content-Type 与 content-type 含义相同。Title-Case 仅为约定写法。
Host 请求头有什么用？: Host 告知服务器请求指向哪个域名。HTTP/1.1 中必填，使一台服务器可按名称托管多个网站。
缓存如何用请求头实现？: Cache-Control 规定响应可缓存多久；ETag 与 If-None-Match 让客户端询问“内容变了吗？”，未变则返回轻量的 304。