StatusDetector

HTTP Status Codes

An HTTP status code is a three-digit number returned by a web server in the first line of its response. The first digit groups the meaning: 1xx informational, 2xx success, 3xx redirection, 4xx client error, 5xx server error.

Every code below is explained in plain English with what it means, what to do when you see it, and how long similar issues typically last.

Looking for a status message that is not an HTTP code? Use the Status Meaning Decoder →

1xx Informational

2 codes

The server received the request and is continuing to process it. You rarely see these in normal browsing.

100Continue

The server has received the request headers and the client should proceed to send the body.

101Switching Protocols

The server agrees to switch protocols as requested by the client (e.g., upgrading to WebSocket).

2xx Success

4 codes

The request was received, understood, and processed successfully.

200OK

The request succeeded. The server returned the expected response.

201Created

The request succeeded and a new resource was created as a result — common after POST requests.

204No Content

The server fulfilled the request but has no content to return — common for DELETE or action endpoints.

206Partial Content

The server is delivering only part of the resource due to a range request (used in video streaming).

3xx Redirection

5 codes

The resource has moved or the client needs to take additional action — usually following a redirect.

301Moved Permanently

The URL has moved to a new address permanently. Browsers and search engines should update their links.

302Found

The URL temporarily redirects to another location. Browsers follow the redirect but should keep the original URL.

304Not Modified

The resource has not changed since the last request. The browser can use its cached version.

307Temporary Redirect

Same as 302 but the HTTP method must not change when following the redirect.

308Permanent Redirect

Same as 301 but the HTTP method must not change when following the redirect.

4xx Client Error

11 codes

The request was bad, unauthorized, or asked for something that does not exist. The fix usually starts on the client side.

400Bad Request

The server could not understand the request due to malformed syntax, invalid data, or a missing required parameter.

401Unauthorized

Authentication is required and has failed or has not been provided. Log in first.

403Forbidden

You are authenticated but do not have permission to access this resource.

404Not Found

The server could not find the requested URL. The page may have been deleted or the link may be wrong.

405Method Not Allowed

The HTTP method used (GET, POST, DELETE, etc.) is not supported for this endpoint.

408Request Timeout

The server timed out waiting for the rest of the request from the client.

409Conflict

The request conflicts with the current state of the server — often a duplicate resource or version mismatch.

410Gone

The resource has been permanently removed from the server, and no forwarding address is known.

422Unprocessable Entity

The request was well-formed but the server was unable to process it due to semantic errors — common in form validation.

429Too Many Requests

You have sent too many requests in a given time. Slow down — the server is rate limiting you.

451Unavailable For Legal Reasons

The resource is blocked for legal reasons — such as government-mandated censorship or a court order.

5xx Server Error

7 codes

The server understood the request but failed to handle it. The site is having problems on its end.

500Internal Server Error

Something went wrong on the server. The problem is on their end, not yours.

501Not Implemented

The server does not support the functionality needed to fulfill the request.

502Bad Gateway

A server acting as a proxy received an invalid response from an upstream server. Often a sign of an overloaded backend.

503Service Unavailable

The server is temporarily unable to handle requests — it may be overloaded or down for maintenance.

504Gateway Timeout

A proxy or gateway did not receive a response from the upstream server in time.

507Insufficient Storage

The server is unable to store the data needed to complete the request.

508Loop Detected

The server detected an infinite loop while processing the request.

How to test what a real site is returning

If you are seeing one of these codes on a specific website, the StatusDetector Website Down Checker probes the URL from our servers and reports the actual HTTP status, DNS resolution, SSL certificate, and response latency.

Open the Website Down Checker

Frequently asked

What is an HTTP status code?

An HTTP status code is a three-digit number returned by a web server in response to a request. It tells you whether the request succeeded (2xx), was redirected (3xx), failed because of the request (4xx), or failed because of the server (5xx).

What is the difference between a 4xx and a 5xx error?

A 4xx error means the request itself was the problem — bad URL, missing credentials, or asking for something that does not exist. A 5xx error means the server received your request but failed to handle it. 4xx is on you (or your client); 5xx is on them.

Why am I seeing the same error on multiple sites?

If you see network-level errors (like ERR_CONNECTION_REFUSED or NXDOMAIN) on multiple sites at once, the problem is probably your network or DNS. If you see a 5xx code from many sites that all share infrastructure (like Cloudflare), it is more likely an upstream provider outage.

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