🚦 HTTP Status Code Reference
By ToolNimba Web Dev Team · Updated 2026-06-19
Showing all status codes.
Every time a browser or app talks to a web server, the server answers with a three-digit HTTP status code that says how the request went. This reference lists the codes you will actually meet, from 1xx through 5xx, with a plain-English name and meaning for each. Type a number like 404, a word like timeout, or a class like 5xx into the search box, and the list filters instantly. Use the class buttons to jump straight to client errors or server errors.
What is the HTTP Status Codes?
An HTTP status code is a short numeric reply that a server sends with every response. The first digit puts the code into one of five classes, so you can tell at a glance what kind of answer you are getting. 1xx codes are informational, 2xx mean success, 3xx mean a redirect is needed, 4xx mean the client (the request) got something wrong, and 5xx mean the server itself failed. Knowing just the first digit is often enough to point you in the right direction.
The codes are defined by the Internet standards bodies (the IETF) and reused across the whole web, so a 404 means the same thing whether it comes from a tiny blog or a global API. That shared vocabulary is what lets browsers, caches, search-engine crawlers, and monitoring tools all react sensibly without custom rules for each site. A correct status code is not just cosmetic: search engines treat a 200, a 301, and a 404 very differently, and a page that returns the wrong code can be indexed or dropped incorrectly.
The most useful skill is matching a symptom to a class. A broken link is almost always a 404. A login wall is a 401 or 403. A site that loads but the API behind it is down often shows a 502 or 503 because a gateway or proxy could not reach the real server. Once you know the class, the exact code (and the meaning shown here) tells you whether the fix belongs on your side or the server side.
When to use it
- Looking up what a code like 404, 403, or 502 means while debugging a failing request.
- Choosing the correct status code to return from your own API or web server (for example 201 after creating a record, or 422 for a validation error).
- Explaining to a teammate or client why a page returns the code it does, and whose side the fix is on.
- Checking redirect behaviour, such as the difference between a permanent 301 and a temporary 302 or 307.
- Teaching or revising the HTTP status code families for an interview or certification.
How to use the HTTP Status Codes
- Type a code number, a name, or a keyword into the search box (for example 404, not found, or redirect).
- Or click a class button (1xx through 5xx) to show only codes in that family.
- Read the matching codes, grouped by class, each with its official name and a short meaning.
- Combine search and a class filter to narrow a large family quickly, then clear the box to see everything again.
Formula & method
Worked examples
A visitor clicks a link on your site and sees an error page saying the page does not exist.
- The server could not find the requested URL, so it returns a code in the 4xx (client error) class.
- The specific code is 404 Not Found, meaning the resource is missing or the URL is mistyped.
- Because it is a 4xx, the problem is with the request (a wrong or dead link), not the server itself.
Result: The link points to a missing page and should be fixed or redirected with a 301.
Your app loads but its API calls all fail, and the network tab shows code 503.
- 503 starts with 5, so it is a server-error class code, not a problem with your request.
- 503 Service Unavailable means the server is overloaded or down for maintenance.
- The fix is on the server side, retry later or check the backend, rather than changing the request.
Result: The backend is temporarily unavailable, so wait and retry instead of editing the client.
The five HTTP status code classes at a glance
| Class | Range | Meaning | Typical example |
|---|---|---|---|
| 1xx | 100 to 199 | Informational, request received and continuing | 100 Continue |
| 2xx | 200 to 299 | Success, the request was completed | 200 OK |
| 3xx | 300 to 399 | Redirection, more action is needed | 301 Moved Permanently |
| 4xx | 400 to 499 | Client error, the request was faulty | 404 Not Found |
| 5xx | 500 to 599 | Server error, the server failed | 500 Internal Server Error |
Commonly confused codes and how they differ
| Code | Name | Key point |
|---|---|---|
| 301 | Moved Permanently | Permanent redirect, search engines transfer ranking to the new URL |
| 302 | Found | Temporary redirect, keep using the original URL in future |
| 401 | Unauthorized | You are not authenticated, log in first |
| 403 | Forbidden | You are authenticated but not allowed access |
| 502 | Bad Gateway | An upstream server gave a gateway an invalid response |
| 504 | Gateway Timeout | An upstream server did not respond to a gateway in time |
Common mistakes to avoid
- Returning 200 for an error page. A friendly error page that still sends a 200 OK code tells crawlers and tools the page worked. Missing pages should return 404 (or 410 if gone for good) so they are handled correctly.
- Confusing 401 and 403. A 401 means you have not proven who you are, so logging in may help. A 403 means the server knows who you are and still refuses, so more credentials will not change anything.
- Using 302 when you mean 301. A 302 is a temporary redirect, so search engines keep indexing the old URL. For a permanent move use 301 (or 308) so ranking and links transfer to the new address.
- Blaming the client for a 5xx. Any code starting with 5 is a server-side failure. Re-sending the same request rarely helps until the server or its upstream gateway is fixed.
Glossary
- Status code
- The three-digit number a server returns with every HTTP response to describe the outcome of the request.
- Class
- The family a code belongs to, set by its first digit: 1, 2, 3, 4, or 5.
- Client error
- A 4xx code, meaning the request itself was wrong, such as a missing page or bad input.
- Server error
- A 5xx code, meaning the server failed to handle an otherwise valid request.
- Redirect
- A 3xx code that tells the client to fetch the resource from a different URL.
- Gateway
- A server such as a proxy or load balancer that forwards a request to another (upstream) server and relays its response.
Frequently asked questions
What is a 404 error?
404 Not Found is a client-error code that means the server could not find the requested resource. It usually points to a broken or mistyped link, a deleted page, or a wrong URL. The fix is to correct the link or set up a redirect to a working page.
What do the five status code classes mean?
The first digit sets the class. 1xx is informational, 2xx is success, 3xx means a redirect is needed, 4xx is a client error (the request was wrong), and 5xx is a server error (the server failed). Knowing the class alone often tells you whose side the problem is on.
What is the difference between 301 and 302?
A 301 Moved Permanently says the resource has a new permanent URL, and search engines transfer ranking to it. A 302 Found (and 307) is a temporary redirect, so the original URL should still be used in future and ranking stays with it.
What is the difference between 401 and 403?
A 401 Unauthorized means you have not authenticated, so providing valid credentials may grant access. A 403 Forbidden means the server understood who you are and still refuses, so logging in again will not help.
What does a 500 error mean?
500 Internal Server Error is a generic server-side failure: the server hit an unexpected condition and could not complete the request. Because it is a 5xx code, the fix belongs on the server, not in the request you sent.
Is my data sent anywhere when I use this reference?
No. This tool is a static list of HTTP status codes that runs entirely in your browser. Searching and filtering happen locally with no network calls, so nothing you type is sent to any server.