HTTPステータスコード
すべてのHTTPステータスコードとその意味のクイックリファレンス
61 / 61 status codes
Continue
The server has received the request headers and the client should proceed to send the request body.
Switching Protocols
The requester has asked the server to switch protocols and the server has agreed to do so.
Processing
The server has received and is processing the request, but no response is available yet.
Early Hints
Used to return some response headers before final HTTP message.
OK
The request has succeeded. The meaning depends on the HTTP method used.
Created
The request has been fulfilled and a new resource has been created.
Accepted
The request has been accepted for processing, but the processing has not been completed.
Non-Authoritative Information
The returned metadata is not exactly the same as available from the origin server.
No Content
The server successfully processed the request but is not returning any content.
Reset Content
The server successfully processed the request and is asking the requester to reset the document view.
Partial Content
The server is delivering only part of the resource due to a range header sent by the client.
Multi-Status
The message body contains multiple status codes for multiple independent operations.
Already Reported
The members of a DAV binding have already been enumerated in a previous reply.
IM Used
The server has fulfilled a request for the resource, and the response represents one or more instance-manipulations.
Multiple Choices
The request has more than one possible response. The user should choose one of them.
Moved Permanently
The URL of the requested resource has been changed permanently. The new URL is given in the response.
Found
The URI of the requested resource has been changed temporarily. Further changes might be made in the future.
See Other
The server sent this response to direct the client to get the requested resource at another URI with a GET request.
Not Modified
The resource has not been modified since the last request. The client can use the cached version.
Use Proxy
The requested resource must be accessed through the proxy given by the Location field. (Deprecated)
Temporary Redirect
The server sends this response to redirect the client with the same HTTP method as the prior request.
Permanent Redirect
The resource is permanently located at another URI, specified by the Location header. Same method must be used.
Bad Request
The server cannot or will not process the request due to something perceived to be a client error.
Unauthorized
The client must authenticate itself to get the requested response. Similar to 403 but authentication is possible.
Payment Required
Reserved for future use. Originally created for digital payment systems.
Forbidden
The client does not have access rights to the content. Unlike 401, the client's identity is known to the server.
Not Found
The server cannot find the requested resource. This is the most common error response on the web.
Method Not Allowed
The request method is known by the server but is not supported by the target resource.
Not Acceptable
The server cannot produce a response matching the list of acceptable values defined in the request headers.
Proxy Authentication Required
The client must first authenticate itself with the proxy.
Request Timeout
The server would like to shut down this unused connection. Sent on an idle connection by some servers.
Conflict
The request conflicts with the current state of the server.
Gone
The content has been permanently deleted from the server, with no forwarding address.
Length Required
The server rejected the request because the Content-Length header field is not defined.
Precondition Failed
The client has indicated preconditions in its headers which the server does not meet.
Payload Too Large
The request entity is larger than limits defined by the server.
URI Too Long
The URI requested by the client is longer than the server is willing to interpret.
Unsupported Media Type
The media format of the requested data is not supported by the server.
Range Not Satisfiable
The range specified by the Range header field in the request cannot be fulfilled.
Expectation Failed
The expectation indicated by the Expect request header field cannot be met by the server.
I'm a Teapot
The server refuses the attempt to brew coffee with a teapot. (RFC 2324, an April Fools' joke)
Unprocessable Entity
The request was well-formed but was unable to be followed due to semantic errors.
Locked
The resource that is being accessed is locked.
Failed Dependency
The request failed because it depended on another request and that request failed.
Too Early
The server is unwilling to risk processing a request that might be replayed.
Upgrade Required
The server refuses to perform the request using the current protocol but might be willing to after the client upgrades.
Precondition Required
The origin server requires the request to be conditional to prevent lost update conflicts.
Too Many Requests
The user has sent too many requests in a given amount of time (rate limiting).
Request Header Fields Too Large
The server is unwilling to process the request because its header fields are too large.
Unavailable For Legal Reasons
The user agent requested a resource that cannot legally be provided.
Internal Server Error
The server has encountered a situation it does not know how to handle.
Not Implemented
The request method is not supported by the server and cannot be handled.
Bad Gateway
The server acting as a gateway got an invalid response from the upstream server.
Service Unavailable
The server is not ready to handle the request. Common causes are maintenance or overload.
Gateway Timeout
The server acting as a gateway did not get a response in time from the upstream server.
HTTP Version Not Supported
The HTTP version used in the request is not supported by the server.
Variant Also Negotiates
The server has an internal configuration error: transparent content negotiation results in a circular reference.
Insufficient Storage
The server is unable to store the representation needed to complete the request.
Loop Detected
The server detected an infinite loop while processing the request.
Not Extended
Further extensions to the request are required for the server to fulfill it.
Network Authentication Required
The client needs to authenticate to gain network access (e.g., captive portal).
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HTTP Status Codes: The Complete Reference Guide
Key Takeaways
- HTTP status codes are grouped into five classes: 1xx (informational), 2xx (success), 3xx (redirection), 4xx (client error), and 5xx (server error).
- Choosing the correct status code for API responses is critical for proper client behavior, caching, and debugging.
- This reference tool runs entirely in your browser — no network requests are made.
HTTP status codes are the standardized response language between web servers and clients. Every API response, page load, and resource request includes a status code that tells the client exactly what happened. Understanding these codes is essential for building robust APIs, debugging network issues, and implementing proper error handling in web applications.
There are 63 officially registered HTTP status codes defined across multiple RFCs, with 5 major classes.
Standard Codes
Key Concepts
2xx Success Codes
200 OK (standard success), 201 Created (resource created), 204 No Content (success with empty body), 206 Partial Content (range request). Each has specific semantics for proper API design.
3xx Redirection Codes
301 Moved Permanently (SEO-safe redirect), 302 Found (temporary redirect), 304 Not Modified (cache validation), 307 Temporary Redirect (preserves HTTP method).
4xx Client Error Codes
400 Bad Request (malformed syntax), 401 Unauthorized (authentication required), 403 Forbidden (access denied), 404 Not Found, 429 Too Many Requests (rate limiting).
5xx Server Error Codes
500 Internal Server Error (generic failure), 502 Bad Gateway (upstream failure), 503 Service Unavailable (temporary overload), 504 Gateway Timeout (upstream timeout).
Pro Tips
Use 201 Created (not 200) when a POST request successfully creates a resource — include a Location header pointing to the new resource.
Return 429 Too Many Requests with a Retry-After header when rate limiting — this tells clients exactly when to retry.
Use 401 for missing/invalid authentication and 403 for valid authentication but insufficient permissions — they have different meanings.
Avoid using 200 with an error message in the body — this anti-pattern breaks error handling in HTTP clients and monitoring tools.
This HTTP status code reference runs entirely in your browser with no network requests. All content is bundled locally for instant access.