HTTP_status.md

HTTP Status Codes

Simple workflow

1. Every time a browser or app sends a request to a server, the server replies with a status code — a 3-digit number telling you what happened
2. The first digit tells you the category (1xx = info, 2xx = success, 3xx = redirect, 4xx = client error, 5xx = server error)
3. Browsers/apps use this code to decide what to do next — show the page, redirect, retry, or show an error message

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1__ -> Informational

Request received, still processing.

Code	Name	Meaning
100	Continue	Server got the request headers; client should send the body.
101	Switching Protocols	Server agrees to switch protocols (e.g., HTTP → WebSocket).
102	Processing	Server is still working, prevents client timeout (WebDAV).
103	Early Hints	Lets the client start preloading resources before the final response is ready.
104	Upload Resumption Supported	Temporary/experimental — signals support for resuming interrupted uploads.

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2__ -> Success

The request worked as intended.

Code	Name	Meaning
200	OK	Standard success response — request worked, here's the data.
201	Created	Request succeeded and a new resource was created (e.g., after a POST).
202	Accepted	Request accepted but not finished processing yet.
203	Non-Authoritative Information	Success, but the data came from a copy/proxy, not the original source.
204	No Content	Success, but there's nothing to send back (e.g., after a DELETE).
205	Reset Content	Success; tells the client to reset the view/form that sent the request.
206	Partial Content	Server sent only part of the resource (used for video streaming/downloads).
207	Multi-Status	Response covers multiple sub-requests, each with its own status (WebDAV).
208	Already Reported	Avoids repeating the same binding info multiple times (WebDAV).
226	IM Used	Server fulfilled the request via one or more instance-manipulations.

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3__ -> Redirection

You need to go somewhere else to complete the request.

Code	Name	Meaning
300	Multiple Choices	More than one option exists for the resource; client/user must pick one.
301	Moved Permanently	Resource has a new permanent URL; update your bookmarks/links.
302	Found	Resource is temporarily at a different URL.
303	See Other	Fetch the result from a different URL using a GET request.
304	Not Modified	Cached version is still valid; no need to re-download.
305	Use Proxy	(Deprecated) Resource must be accessed through the specified proxy.
306	Unused	Reserved; no longer used.
307	Temporary Redirect	Same as 302 but guarantees the request method won't change.
308	Permanent Redirect	Same as 301 but guarantees the request method won't change.

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4__ -> Client Errors

Something's wrong with the request itself (the sender's fault).

Code	Name	Meaning
400	Bad Request	Server can't understand the request — malformed syntax.
401	Unauthorized	You need to log in / provide valid credentials first.
402	Payment Required	Reserved for future use — originally meant for digital payment systems, rarely used, sometimes seen on paywalled APIs.
403	Forbidden	Server understood the request but refuses — you don't have permission.
404	Not Found	The requested resource doesn't exist on the server.
405	Method Not Allowed	The HTTP method used (GET/POST/etc.) isn't allowed for this resource.
406	Not Acceptable	Server can't return a response matching the formats the client will accept.
407	Proxy Authentication Required	Like 401, but you need to authenticate with a proxy first.
408	Request Timeout	Server timed out waiting for the request.
409	Conflict	Request conflicts with the current state of the resource (e.g., edit conflict).
410	Gone	Resource used to exist but was permanently removed.
411	Length Required	Server requires a Content-Length header that's missing.
412	Precondition Failed	A condition set in the request headers wasn't met.
413	Content Too Large	The request body is too big for the server to process.
414	URI Too Long	The requested URL is too long for the server to process.
415	Unsupported Media Type	The request body's format isn't supported (e.g., sending XML when server expects JSON).
416	Range Not Satisfiable	The requested byte range can't be provided (e.g., asking for bytes past file end).
417	Expectation Failed	Server can't meet the requirement in the request's Expect header.
418	(Unused)	Historically "I'm a Teapot" — an April Fools' joke code from an old RFC; officially unused now.
421	Misdirected Request	Request was sent to a server that can't produce a valid response for it.
422	Unprocessable Content	Syntax is fine, but the server can't process the contained instructions.
423	Locked	The resource being accessed is locked (WebDAV).
424	Failed Dependency	Request failed because a previous related request failed (WebDAV).
425	Too Early	Server is unwilling to process a request that might be replayed.
426	Upgrade Required	Client should switch to a different protocol (server will specify which).
428	Precondition Required	Server requires the request to be conditional (to prevent lost updates).
429	Too Many Requests	You've hit a rate limit — slow down and try again later.
431	Request Header Fields Too Large	Header(s) are too big for the server to process.
451	Unavailable For Legal Reasons	Content blocked due to a legal demand (e.g., government takedown).

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5__ -> Server Errors

Something's wrong on the server side (not your fault).

Code	Name	Meaning
500	Internal Server Error	Generic "something broke" error on the server.
501	Not Implemented	Server doesn't support the functionality needed to fulfill the request.
502	Bad Gateway	A server acting as a proxy/gateway got an invalid response from an upstream server.
503	Service Unavailable	Server is temporarily overloaded or down for maintenance.
504	Gateway Timeout	A proxy/gateway server didn't get a response in time from the upstream server.
505	HTTP Version Not Supported	Server doesn't support the HTTP version used in the request.
506	Variant Also Negotiates	Server has an internal content-negotiation configuration error.
507	Insufficient Storage	Server can't store the representation needed to complete the request (WebDAV).
508	Loop Detected	Server detected an infinite loop while processing the request (WebDAV).
510	Not Extended (Obsoleted)	Further extensions to the request are required; this status is now historic.
511	Network Authentication Required	You need to authenticate to gain network access (e.g., a Wi-Fi login page).

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Quick memory trick

• 1xx → "Hold on..."
• 2xx → "All good ✅"
• 3xx → "Go elsewhere ↪️"
• 4xx → "You messed up 🙅"
• 5xx → "We messed up 🔧"

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Source: IANA — (HTTP) Status Code Registry Each of this information is get from this website for more knowledge visit them