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HTTP 状态码参考

从 100 Continue 到 511 Network Authentication Required 的 60+ 标准 HTTP 响应码，每条附一行概要、RFC 引用、推荐用法，以及对常被误用的码（401 vs 403、301 永久缓存、400 vs 422 等）的「陷阱」提示。按分类（1xx 信息、2xx 成功、3xx 重定向、4xx 客户端、5xx 服务器）过滤，或在码值、名称、概要、备注中全文搜索。

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结果数: 61

  • 100Continue

    Server received headers; client should send the body.

    RFC: RFC 9110 §15.2.1

  • 101Switching Protocols

    Server agrees to switch protocols (e.g., HTTP/2, WebSocket).

    使用时机: WebSocket upgrade handshakes.

    RFC: RFC 9110 §15.2.2

  • 102Processing

    WebDAV: request received but no response yet.

    RFC: RFC 2518

  • 103Early Hints

    Preload hints sent before the final response.

    使用时机: Send Link: rel=preload for critical assets before the slow backend reply lands.

    RFC: RFC 8297

  • 200OK

    Standard success response with a body.

    RFC: RFC 9110 §15.3.1

  • 201Created

    Resource was created; include Location header pointing to it.

    使用时机: POST that creates a new resource. Body is optional.

    RFC: RFC 9110 §15.3.2

  • 202Accepted

    Request accepted for async processing; no result yet.

    使用时机: Long-running jobs — return a status URL for the client to poll.

    RFC: RFC 9110 §15.3.3

  • 203Non-Authoritative Information

    Response was transformed by a proxy.

    RFC: RFC 9110 §15.3.4

  • 204No Content

    Success but no body to send.

    使用时机: DELETE success, PUT with no useful body, preflight OK.

    陷阱: MUST NOT include a message body. Some libraries error if you do.

    RFC: RFC 9110 §15.3.5

  • 205Reset Content

    Success; client should reset the document view (clear form).

    RFC: RFC 9110 §15.3.6

  • 206Partial Content

    Range request was honored; partial body follows.

    使用时机: Resumable downloads, video seek.

    RFC: RFC 9110 §15.3.7

  • 207Multi-Status

    WebDAV multi-resource batched results.

    RFC: RFC 4918

  • 208Already Reported

    WebDAV: bindings already enumerated earlier in the response.

    RFC: RFC 5842

  • 226IM Used

    Delta encoding response.

    RFC: RFC 3229

  • 300Multiple Choices

    Multiple resources match; client should pick one.

    RFC: RFC 9110 §15.4.1

  • 301Moved Permanently

    Resource has a new permanent URL. Caches forever.

    使用时机: Domain migration, URL restructure.

    陷阱: Browsers cache 301 aggressively — fixing a wrong one is painful. Test with 302 first.

    RFC: RFC 9110 §15.4.2

  • 302Found

    Temporary redirect (legacy semantics, method may change).

    陷阱: Historically rewrote POST→GET. Use 303 or 307 for explicit method-preservation semantics.

    RFC: RFC 9110 §15.4.3

  • 303See Other

    Redirect that always becomes a GET.

    使用时机: POST/Redirect/GET pattern after form submit.

    RFC: RFC 9110 §15.4.4

  • 304Not Modified

    Conditional request: cached copy is still fresh.

    使用时机: Response to If-None-Match / If-Modified-Since.

    陷阱: MUST NOT include a body.

    RFC: RFC 9110 §15.4.5

  • 307Temporary Redirect

    Temporary; method and body must be preserved.

    RFC: RFC 9110 §15.4.8

  • 308Permanent Redirect

    Permanent; method and body must be preserved.

    使用时机: POSTs that must survive a permanent move. Prefer over 301 for API endpoints.

    RFC: RFC 9110 §15.4.9

  • 400Bad Request

    Generic malformed request the server cannot parse.

    陷阱: Don't use 400 for valid syntax with bad semantics — use 422 instead.

    RFC: RFC 9110 §15.5.1

  • 401Unauthorized

    Authentication required or failed. Must include WWW-Authenticate.

    陷阱: Misnamed historically — means "unauthenticated". Use 403 for "authenticated but not allowed".

    RFC: RFC 9110 §15.5.2

  • 402Payment Required

    Reserved for future use; some APIs use for billing failures.

    RFC: RFC 9110 §15.5.3

  • 403Forbidden

    Authenticated but the action is not allowed for this principal.

    使用时机: Authorization failure, geo-block, or "you cannot do this regardless of auth".

    RFC: RFC 9110 §15.5.4

  • 404Not Found

    Resource does not exist (or you are hiding it).

    使用时机: Often returned instead of 403 to avoid disclosing existence.

    RFC: RFC 9110 §15.5.5

  • 405Method Not Allowed

    Resource exists but does not support this verb. MUST include Allow header.

    RFC: RFC 9110 §15.5.6

  • 406Not Acceptable

    No representation matches the Accept headers.

    RFC: RFC 9110 §15.5.7

  • 407Proxy Authentication Required

    Like 401 but for proxies. Must include Proxy-Authenticate.

    RFC: RFC 9110 §15.5.8

  • 408Request Timeout

    Server gave up waiting for the request to finish.

    RFC: RFC 9110 §15.5.9

  • 409Conflict

    Request collides with current state (e.g., edit conflict, duplicate).

    使用时机: Unique-key violations on creation, version mismatch on update.

    RFC: RFC 9110 §15.5.10

  • 410Gone

    Resource permanently removed with no forwarding address.

    使用时机: Use over 404 when you want crawlers/clients to drop the URL permanently.

    RFC: RFC 9110 §15.5.11

  • 411Length Required

    Server requires Content-Length and the request omitted it.

    RFC: RFC 9110 §15.5.12

  • 412Precondition Failed

    If-Match / If-Unmodified-Since check failed.

    使用时机: Optimistic concurrency control on updates.

    RFC: RFC 9110 §15.5.13

  • 413Content Too Large

    Body exceeds the server limit. Formerly "Payload Too Large".

    RFC: RFC 9110 §15.5.14

  • 414URI Too Long

    URL exceeds server limit (commonly ~8KB).

    RFC: RFC 9110 §15.5.15

  • 415Unsupported Media Type

    Content-Type is not supported by this endpoint.

    RFC: RFC 9110 §15.5.16

  • 416Range Not Satisfiable

    Range header asks for bytes outside the resource.

    RFC: RFC 9110 §15.5.17

  • 417Expectation Failed

    Server cannot meet the Expect: header requirements.

    RFC: RFC 9110 §15.5.18

  • 418I'm a teapot

    April-fools status (RFC 2324). Returned by some debugging or honeypot endpoints.

    RFC: RFC 2324

  • 421Misdirected Request

    Request was routed to a server that cannot produce a response (e.g., wrong SNI).

    RFC: RFC 9110 §15.5.20

  • 422Unprocessable Content

    Syntactically valid but semantically incorrect (e.g., validation failure).

    使用时机: Form-level validation errors on a JSON API.

    RFC: RFC 9110 §15.5.21

  • 423Locked

    WebDAV: resource is locked.

    RFC: RFC 4918

  • 424Failed Dependency

    WebDAV: a previous request in the chain failed.

    RFC: RFC 4918

  • 425Too Early

    Server refuses replay-vulnerable early data (TLS 1.3 0-RTT).

    RFC: RFC 8470

  • 426Upgrade Required

    Client must upgrade to a different protocol. Include Upgrade header.

    RFC: RFC 9110 §15.5.22

  • 428Precondition Required

    Server requires the request to be conditional (If-Match etc).

    使用时机: APIs that demand optimistic-concurrency tokens to prevent lost updates.

    RFC: RFC 6585

  • 429Too Many Requests

    Rate-limited. Include Retry-After header.

    RFC: RFC 6585

  • 431Request Header Fields Too Large

    Sum of headers exceeds the server limit.

    RFC: RFC 6585

  • 451Unavailable For Legal Reasons

    Blocked due to legal demand (Fahrenheit 451 reference).

    RFC: RFC 7725

  • 500Internal Server Error

    Unhandled exception or generic server crash.

    陷阱: Never expose stack traces — log them server-side only.

    RFC: RFC 9110 §15.6.1

  • 501Not Implemented

    Server does not support the requested method at all.

    RFC: RFC 9110 §15.6.2

  • 502Bad Gateway

    Upstream returned an invalid response to the gateway.

    使用时机: Load balancer cannot reach origin; origin returned junk.

    RFC: RFC 9110 §15.6.3

  • 503Service Unavailable

    Server temporarily down or overloaded. Should include Retry-After.

    RFC: RFC 9110 §15.6.4

  • 504Gateway Timeout

    Gateway gave up waiting for upstream.

    RFC: RFC 9110 §15.6.5

  • 505HTTP Version Not Supported

    Server does not support the HTTP version in the request.

    RFC: RFC 9110 §15.6.6

  • 506Variant Also Negotiates

    Transparent content negotiation is misconfigured.

    RFC: RFC 2295

  • 507Insufficient Storage

    WebDAV: server cannot store the representation.

    RFC: RFC 4918

  • 508Loop Detected

    WebDAV: infinite loop while processing.

    RFC: RFC 5842

  • 510Not Extended

    Further extensions required to fulfill the request.

    RFC: RFC 2774

  • 511Network Authentication Required

    Captive portal: log in to the network first.

    使用时机: Public Wi-Fi splash pages.

    RFC: RFC 6585

使用方法

  1. 在搜索框输入代码、名称或任意词（例如「redirect」「rate limit」「422」）。
  2. 可用彩色标签按分类过滤。
  3. 查看每条结果的概要、使用时机、陷阱以及 RFC 引用。

常见问题

为什么有些码会标「陷阱」？
少数状态码长期被误用。401 实际是「未认证」却常被理解为「未授权」；301 在浏览器里几乎永久缓存；400 vs 422 争议不止。陷阱标注只列出在代码评审与复盘中真正会咬人的具体情况。
包含 WebDAV 码吗？
包含 — 102、207、208、423、424、507、508 及其 RFC。即便你不直接用 WebDAV，库或代理偶尔会返回，了解一下含义有用。
厂商自定义码（Cloudflare 520-527 等）呢？
厂商专用码（Cloudflare 520-527、AWS 460/463、IIS 440）不在内 — 它们不属于任何 RFC，含义因厂商而异，请查相应厂商文档。
为什么有些码没有「使用时机」？
若代码语义在名称上已自明（200 OK、500 Internal Server Error），或仅出现在特殊场景，概要足矣。只有当确实有值得提醒之处时才显示 when / pitfall。

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