An HTTP error code is the three digit number a web server sends back to tell your browser how a request went. When you open a page, the reply carries a number, and the first digit says which side is responsible: 2 means success, 3 means a redirect, 4 means the request has a problem, and 5 means the server has a problem.
This hub explains the whole system and points to a separate guide for every common code, from 404 and 500 to the extra numbers used by one CDN provider. Use it to learn who has to act next, you or the website owner, and to find the right fix without guessing. The list also covers the less common numbers people search for, such as 301, 412, 417 and 505.
Common causes
1A mistyped or outdated web address
How to tellOnly one page fails, the rest of the site opens normally
What fixes itCheck the address, then go to the home page and search from there
2You are not signed in or not allowed
How to tellMessage mentions login, permission or access
What fixes itSign in again with the right account, or ask the owner for access
3The server is overloaded or in maintenance
How to tellMany pages are slow, 5xx numbers, error clears with time
What fixes itWait a few minutes and reload once; check from another network
4A broken script or setting on the site
How to tell500 type errors that appear for every visitor
What fixes itOnly the site owner can fix it; report it and try later
5Too many requests from your network
How to tellError appears after repeated refreshing or from a shared connection
What fixes itStop refreshing, wait a while, or switch to mobile data
6Large upload or odd request data
How to tellError shows only when sending a file or a long form
What fixes itReduce the file size or the form content and send again
Where to start
Read the number and its first digit
Look at the first digit. A 4xx number means the request was wrong or refused. A 5xx number means the server failed while handling a fair request. A 3xx number is only a redirect and usually fixes itself.
Reload once after a short wait
Give it a minute, then reload with F5 on a PC or a swipe down on a phone. Refreshing repeatedly is a common reason for a later 429 error.
Check the address character by character
For 400, 404 and 414 errors, look for a stray space, a missing letter or a very long copied link with extra tracking text. Remove everything after the question mark and try again.
Try a private window
Try the link inside a private tab. If it opens there, an old cookie or cached file is the problem, so clear the data for that one site in your browser settings.
Test on another network or device
Load the page over mobile data, or ask a friend. If it fails for them as well, the website is down or broken and only its owner can fix it. If it works, the trouble sits on your device or network.
Sign in again for 401 and 403
Log out, sign in again and make sure you are using the account that has permission. Some pages also block certain regions or networks, so a second network is a fair test.
Report the error to the site owner
If nothing helps, send the owner the web address, the exact number and the time you saw it. Server side errors need their log to be read, which only they can do.
What an HTTP error code tells you, in simple terms
Picture a shop counter. You ask for something, and the clerk answers with a short code before anything else. "200" means here it is. "404" means we do not have that. "503" means the stockroom is closed right now. The browser reads the number and decides what to show, and the page text you see is only a friendly version of the same answer.
You tap a saved link and see 404 Not Found. The server is working, it simply has no page at that address, so a fix on your phone will not help. Look for the page from the site's home page instead.
Full guides for each common code
Open the guide that matches your number. Each one gives the meaning, the causes, the fix for visitors and the fix for site owners.
| Guide | What it covers |
|---|---|
| 200 OK | The request worked and the page or data came back. |
| 201 Created | A new record or file was made on the server. |
| 204 No Content | Success, but there is nothing to show in reply. |
| 302 Found (redirect) | A temporary jump to another address. |
| 304 Not Modified | Your saved copy is still current, so nothing was resent. |
| 307 Temporary Redirect | A temporary redirect that keeps the same request method. |
| 400 Bad Request | The server could not understand what your browser sent. |
| 401 Unauthorized | You must sign in or send valid credentials. |
| 402 Payment Required | A reserved code, used by some services for payment limits. |
| 403 Forbidden | The server understood you but will not let you in. |
| 404 Not Found | The page does not exist at this address. |
| 405 Method Not Allowed | The address does not accept that kind of request. |
| 406 Not Acceptable | No reply is possible in the format your request wanted. |
| 408 Request Timeout | The server gave up waiting for the request to finish. |
| 409 Conflict | Your change conflicts with what is already stored. |
| 410 Gone | Deleted deliberately, and it is not coming back. |
| 413 Content Too Large | The upload or request is bigger than the server allows. |
| 415 Unsupported Media Type | The file or data type sent is not accepted. |
| 422 Unprocessable Content | The request is well formed but the content fails checks. |
| 429 Too Many Requests | Your device made more requests than the site allows. |
| 499 Client Closed Request | The visitor closed the connection first (a non standard code). |
| 500 Internal Server Error | Something broke inside the server. |
| 501 Not Implemented | The site has no support for what you asked it to do. |
| 502 Bad Gateway | A middle server received an invalid answer from the one behind it. |
| 503 Service Unavailable | The server is busy or in maintenance. |
| 504 Gateway Timeout | A middle server timed out while the server behind it stayed silent. |
| Error 520 | A non standard code from one CDN provider: unknown or empty reply. |
| Error 521 | Non standard CDN code: the origin server refused the connection. |
| Error 522 | Non standard CDN code: the connection to the origin timed out. |
| Error 524 | Non standard CDN code: the origin took too long to reply. |
| Error 525 SSL handshake failed | Non standard CDN code: the secure handshake with the origin failed. |
Other status codes and what they mean
These numbers are real and listed in the official registry, but they appear less often in daily browsing. They are handy for developers and for anyone reading an error log.
| Code | Name | Plain meaning |
|---|---|---|
| 100 | Continue | The first part of the request was accepted, send the rest. |
| 101 | Switching Protocols | The server agrees to change the protocol, as with WebSocket. |
| 202 | Accepted | The request was received but the work is not finished yet. |
| 203 | Non-Authoritative Information | The reply was changed by a middle server on the way. |
| 206 | Partial Content | Only part of a file was sent, as in a resumed download or video. |
| 300 | Multiple Choices | More than one possible answer exists. |
| 301 | Moved Permanently | The page has a new permanent address. |
| 303 | See Other | Go to another address to fetch the result, often after a form. |
| 407 | Proxy Authentication Required | A proxy server wants sign-in details first. |
| 411 | Length Required | The request must state its size. |
| 412 | Precondition Failed | A condition set by the request was not met. |
| 414 | URI Too Long | The web address is longer than the server accepts. |
| 417 | Expectation Failed | The server cannot meet the Expect header in the request. |
| 418 | I'm a teapot | A joke code from an old April Fools document, rarely real. |
| 421 | Misdirected Request | The request reached a server that cannot answer for that site. |
| 423 | Locked | The resource is locked and cannot be changed now. |
| 424 | Failed Dependency | This step failed because an earlier step failed. |
| 431 | Request Header Fields Too Large | The headers, often cookies, are too big. |
| 505 | HTTP Version Not Supported | The server does not support the HTTP version used. |
A 301 error code is a notice rather than a fault: it tells browsers and search engines that a page moved for good. A 303 error code is just a hop to another address after a form, and a 202 error code only says the work was accepted for later. A 412 error code or a 417 error code usually shows up in app and API work, not in normal browsing. A 407 error code points to a proxy that needs a login, common on office and school networks. A 505 error code means the server cannot work with the HTTP version your client used, and the site owner or the app developer has to adjust it.
Numbers people search that are not standard HTTP codes
Some searches for an error code are not in the HTTP registry at all. The number 443 is a port used for secure web traffic, so a "443 error code" is normally a connection or certificate problem, not a status. Numbers 520 to 527 and 530 are returned by one CDN provider, while 419, 420, 440 and 444 are used only by particular software or frameworks. A 419 error code often means a page expired in a web form, and a 424 error code says an earlier step failed first, and a 529 is used by some services to say they are overloaded. Codes such as 137 or 550 come from operating systems or mail and file transfer tools. Treat those as hints about the product that showed them.
| Number | Where it really comes from | First thing to try |
|---|---|---|
| 443 | Secure web port, not a status | Check date and time, then try another network |
| 419 | A framework, often an expired form | Reload the form page and submit again |
| 529 | Used by some services for overload | Wait and retry later |
| 137 | Program exit code on some systems | Restart the app or device |
| 550 | Mail or file transfer reply | Check the address or permission |
For site owners: reading 4xx and 5xx patterns
- Many 404 errors after a redesign mean old links need redirects with a 301.
- Rising 5xx numbers mean the server or an application is failing, so read the error log first.
- A burst of 429 means a bot, a script or a busy network is hitting you hard.
- Check the monitoring from outside your own network, because a page can look fine to you and fail for visitors.
Do not hide errors by sending a 200 for a missing page. Search engines then index empty pages, which hurts the site.
Frequently asked questions
What is an HTTP error code?
It is a three digit number a web server sends back to say how it handled a request. Numbers starting with 4 and 5 are the error ones, and they tell you whether the problem is with the request or with the server.
Is a 301 error code a problem?
No. A 301 means the page moved permanently and the browser is sent to the new address. It only becomes a problem when redirects loop or lead to a missing page.
What does a 412 error code or 417 error code mean?
A 412 means a condition in the request was not met, and a 417 means the server cannot meet the expectation the request made. Both are mostly seen in apps and API work rather than normal page visits.
Can I fix a 5xx error myself?
Not directly, because the fault is on the server. You can reload once, test on another network and report it. The site owner has to repair the cause.
Is a 443 error code the same as a 404?
No. 443 is the port number for secure web traffic, not a status. A 404 means the page does not exist. A 443 problem normally points to a certificate or connection issue.