Common HTTP Error Codes
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When there are too many visitors to the server, the following error might appear on your browser.
What we most often encounter is HTTP 4xx and 5xx. So what do they mean?
HTTP 4xx -> Client Errors
| Status Code | Name | Reason |
|---|---|---|
| 400 | Bad Request | The request syntax is incorrect, and the server cannot understand it. |
| 401 | Unauthorized | The user has not been authenticated, and valid credentials are missing. |
| 403 | Forbidden | The user is authenticated but does not have sufficient permissions. |
| 404 | Not Found | The requested resource does not exist (URL error or resource removed). |
| 405 | Method Not Allowed | An HTTP method that is not allowed was used. |
| 408 | Request Timeout | The server timed out waiting for the request. |
| 409 | Conflict | The request conflicts with the current state of the resource. |
| 413 | Payload Too Large | The request payload is too large, exceeding the server’s size limit. |
| 414 | URI Too Long | The requested URI is too long, exceeding the server’s processing capacity. |
| 429 | Too Many Requests | The request rate is too high, triggering the server’s rate limit. |
HTTP 5xx -> Server Errors
| Status Code | Name | Reason |
|---|---|---|
| 500 | Internal Server Error | An unknown internal error occurred on the server. |
| 501 | Not Implemented | The server does not support the requested functionality or method. |
| 502 | Bad Gateway | The gateway or proxy server received an invalid response from upstream. |
| 503 | Service Unavailable | The server is temporarily unavailable (e.g., overloaded or under maintenance). |
| 504 | Gateway Timeout | The gateway or proxy server did not receive a timely response from upstream. |
| 505 | HTTP Version Not Supported | The server does not support the HTTP protocol version used in the request. |
In addition to 4 and 5, HTTP status codes also include other categories. The complete HTTP status code is divided into five categories, each of which has a specific purpose and meaning.
Other Categories of Code
1xx Informational Responses
| Status Code | Name | Reason |
|---|---|---|
| 100 | Continue | The client should continue sending the remainder of the request. |
| 101 | Switching Protocols | The server agrees to switch protocols (e.g., from HTTP to WebSocket). |
| 102 | Processing | The server is processing the request but has not yet completed it. |
| 103 | Early Hints | Provides early hints to help the client preload critical resources. |
2xx Successful Responses
| Status Code | Name | Reason |
|---|---|---|
| 200 | OK | The request was successful, and the response contains the requested data. |
| 201 | Created | The request was successful, and a new resource was created. |
| 202 | Accepted | The request has been accepted but has not yet been processed. |
| 204 | No Content | The request was successful, but there is no content to return. |
| 206 | Partial Content | The server is returning only part of the resource (used for range requests). |
3xx Redirection Messages
| Status Code | Name | Reason |
|---|---|---|
| 300 | Multiple Choices | The resource has multiple options, and the client needs to choose one. |
| 301 | Moved Permanently | The resource has been permanently moved to a new location. |
| 302 | Found | The resource is temporarily located at a different URI. |
| 303 | See Other | The response can be found under a different URI (often used after POST). |
| 304 | Not Modified | The resource has not been modified; the client can use its cached version. |
| 307 | Temporary Redirect | The resource is temporarily located at a different URI (method unchanged). |
| 308 | Permanent Redirect | The resource has been permanently moved to a new location (method unchanged). |