What Are HTTP Status Codes?
HTTP response codes are three-digit numbers generated by a server to respond to a browser’s request. The Internet Assigned Numbers Authority (IANA) maintains the official registry of all statuses.
The first digit defines the status code’s category, which begins with a number between one and five. For example, 1XX shows informational responses, while 5XX displays server error alerts.
On the other hand, the last two are assigned for specific information under a given classification. For example, 404 indicates that the server can’t find the requested resource.
HTTP defines request methods to indicate the desired action for a resource. Each implements a different semantic, but they have some common features, such as safe, idempotent, and cacheable. Here is the list:
- GET – requests a specific resource representation and will only retrieve data.
- HEAD – requests the same response as the GET method but without a message body.
- POST – submits an entity to the specified resource, often changing the server’s state.
- PUT – replaces all resource representations with the request payload.
- DELETE – removes the specified response.
- OPTIONS – explains the communication options for the resource.
- TRACE – performs a message loop-back test along the path to the resource.
- PATCH – applies partial modifications to a resource.
How Are HTTP Status Codes Categorized?
HTTP status codes have five categories based on the server responses sent to the browser:
- 1XX informational – this class indicates that the server received the HTTP request sent by the browser and will continue the process. It is a temporary response, so the client won’t encounter this status code since it’s not the final answer.
- 2XX success – this class indicates that the server received, understood, and processed the request. Subsequently, the browser accepts the expected information.
- 3XX redirection – this class indicates that the server received the request, but the requested content was moved to a different location, so the client will be redirected.
- 4XX client error – this class indicates that the server can’t complete the request because of a client-side error, such as an unavailable page, bad syntax, or authorization problem. The response will explain whether it is a temporary or permanent issue.
- 5XX server error – this class indicates that the server encountered an error and can’t process a valid request. The response will describe the situation and determine whether it is a temporary or permanent problem.
A Complete List of HTTP Status Codes
Here is the complete list of HTTP status codes:
| Status code | Functions |
| 1XX Informational | |
| 100 | Continue |
| 101 | Switching Protocols |
| 102 | Processing |
| 103 | Early Hints |
| 2XX Successful | |
| 200 | OK |
| 201 | Created |
| 202 | Accepted |
| 203 | Non-Authoritative Information |
| 204 | No Content |
| 205 | Reset Content |
| 206 | Partial Content |
| 207 | Multi-Status |
| 208 | Already Reported |
| 226 | IM Used |
| 3XX Redirection | |
| 300 | Multiple Choices |
| 301 | Moved Permanently |
| 302 | Found (Previously: Moved Temporarily) |
| 303 | See Other |
| 304 | Not Modified |
| 305 (Unused) | Previously: Use Proxy |
| 306 (Unused) | Previously: Switch Proxy |
| 307 | Temporary Redirect |
| 308 | Permanent Redirect |
| 4XX Client Error | |
| 400 | Bad Request |
| 401 | Unauthorized |
| 402 | Payment Required |
| 403 | Forbidden |
| 404 | Not Found |
| 405 | Method Not Allowed |
| 406 | Not Acceptable |
| 407 | Proxy Authentication Required |
| 408 | Request Timeout |
| 409 | Conflict |
| 410 | Gone |
| 411 | Length Required |
| 412 | Precondition Failed |
| 413 | Payload Too Large |
| 414 | URI Too Long |
| 415 | Unsupported Media Type |
| 416 | Range Not Satisfiable |
| 417 | Expectation Failed |
| 418 (Unused) | Previously: I’m a Teapot |
| 421 | Misdirected Request |
| 422 | Unprocessable Entity |
| 423 | Locked |
| 424 | Failed Dependency |
| 425 | Too Early |
| 426 | Upgrade Required |
| 428 | Precondition Required |
| 429 | Too Many Requests |
| 431 | Request Header Fields Too Large |
| 451 | Unavailable for Legal Reasons |
| 5XX Server Error | |
| 500 | Internal Server Error |
| 501 | Not Implemented |
| 502 | Bad Gateway |
| 503 | Service Unavailable |
| 504 | Gateway Timeout |
| 505 | HTTP Version Not Supported |
| 506 | Variant Also Negotiates |
| 507 | Insufficient Storage |
| 508 | Loop Detected |
| 510 (Unused) | Not Extended |
| 511 | Network Authentication Required |
