ToolZeno

HTTP Status Code Lookup

Quickly search, browse, understand, and compare HTTP response status codes. Includes framework code snippets (Laravel, Express, Next.js, Spring Boot, ASP.NET), caching rules, and SEO impact.

Quick Lookup:
1001xx

Continue

Initial request headers received; client should proceed to send request body.

RFC 9110
1011xx

Switching Protocols

Server agrees to switch application protocol (e.g. HTTP/1.1 to WebSockets).

RFC 9110
1031xxexperimental

Early Hints

Allows server to return Link headers before final HTTP response is ready to preload assets.

RFC 8297
2002xx

OK

Cacheable

Request succeeded. The payload sent depends on the HTTP method used.

RFC 9110
2012xx

Created

Request succeeded and a new resource was created as a result.

RFC 9110
2022xx

Accepted

Request has been accepted for processing, but processing has not been completed.

RFC 9110
2042xx

No Content

Cacheable

Request succeeded, but server is not returning any content in response body.

RFC 9110
2062xx

Partial Content

Cacheable

Server is delivering only part of resource due to Range header sent by client.

RFC 9110
3013xx

Moved Permanently

Cacheable

The target resource has been assigned a new permanent URI.

RFC 9110
3023xx

Found

The target resource resides temporarily under a different URI.

RFC 9110
3043xx

Not Modified

Cacheable

Resource has not been modified since last request; use cached version.

RFC 9110
3073xx

Temporary Redirect

Target resource resides temporarily under a different URI; HTTP method must not change.

RFC 9110
3083xx

Permanent Redirect

Cacheable

Target resource has been assigned a new permanent URI; HTTP method must not change.

RFC 9110
4004xx

Bad Request

Server cannot process request due to perceived client error (malformed syntax or payload).

RFC 9110
4014xx

Unauthorized

Request requires user authentication; credentials missing or invalid.

RFC 9110
4034xx

Forbidden

Server understands request but refuses to authorize it (insufficient permissions).

RFC 9110
4044xx

Not Found

Cacheable

Server cannot find the requested resource URL.

RFC 9110
4054xx

Method Not Allowed

The HTTP request method is known by server but not supported by target resource.

RFC 9110
4084xx

Request Timeout

Server timed out waiting for the client request to complete.

RFC 9110
4094xx

Conflict

Request could not be completed due to a conflict with current state of resource.

RFC 9110
4104xx

Gone

Cacheable

Target resource is permanently deleted and will not be available again.

RFC 9110
4184xx

I'm a teapot

April Fools joke RFC status code: Server refuses to brew coffee because it is a teapot.

RFC 2324
4194xxextension

Page Expired

CSRF token missing or expired (Laravel Framework Extension Code).

Laravel Framework
4224xx

Unprocessable Content

Server understands content type and syntax, but request contains semantic validation errors.

RFC 9110
4294xx

Too Many Requests

The user has sent too many requests in a given amount of time (rate limited).

RFC 6585
4514xx

Unavailable For Legal Reasons

Cacheable

Server refuses to serve content due to legal demand or court order (named after Fahrenheit 451).

RFC 7725
4994xxextension

Client Closed Request

Client closed the TCP connection while Nginx was processing request.

Nginx Extension
5005xx

Internal Server Error

Server encountered an unexpected condition that prevented it from fulfilling request.

RFC 9110
5025xx

Bad Gateway

Server, while acting as a gateway or proxy, received an invalid response from upstream server.

RFC 9110
5035xx

Service Unavailable

Server is currently unable to handle request due to temporary overload or maintenance.

RFC 9110
5045xx

Gateway Timeout

Server acting as gateway did not receive timely response from upstream server.

RFC 9110
5205xxextension

Web Server Returned an Unknown Error

Origin server returned an empty, unknown, or unexpected response to Cloudflare proxy.

Cloudflare Extension
5215xxextension

Web Server Is Down

Origin web server refused TCP connection from Cloudflare reverse proxy.

Cloudflare Extension
5225xxextension

Connection Timed Out

Cloudflare TCP handshake with origin web server timed out.

Cloudflare Extension

Mastering HTTP Response Status Codes & API Architecture

HTTP Response Status Codes form the core communication backbone of the World Wide Web and modern RESTful APIs. Whenever a client browser, mobile app, or backend microservice issues an HTTP request, the receiving web server responds with a 3-digit status code that indicates the outcome of the request.

Understanding the semantic meaning, caching rules, SEO implications, and framework implementations of HTTP status codes is essential for backend developers, frontend engineers, DevOps administrators, and SEO specialists alike.

The Five HTTP Status Code Classes

1xx Informational (100–199)

Provisional responses sent before the main HTTP payload. Used for protocol upgrades (101 WebSockets) and performance optimizations (103 Early Hints).

2xx Success (200–299)

Indicates the action requested by the client was received, understood, and accepted successfully (200 OK, 201 Created, 204 No Content).

3xx Redirection (300–399)

Further action must be taken by the user-agent to complete the request (301 Permanent Redirect, 302 Found, 304 Not Modified).

4xx Client Error (400–499)

The request contains invalid syntax, missing authentication, or payload validation errors (400 Bad Request, 401 Unauthorized, 404 Not Found, 422 Unprocessable Content).

5xx Server Error (500–599)

The server failed to fulfill an apparently valid request due to an unhandled code crash, database error, or gateway timeout (500 Internal Error, 502 Bad Gateway, 503 Maintenance, 504 Gateway Timeout).

SEO & REST API Best Practices

1. Always Return Proper Semantic Status Codes: Avoid returning 200 OKwith an error message payload (known as "Soft 200"). Search crawlers will mistakenly index soft 200 error pages.

2. Use 503 for Scheduled Maintenance: When performing deployment maintenance, always return 503 Service Unavailable with a Retry-After header to preserve search engine crawl budget without de-indexing pages.

3. Prefer 422 for Form Validation: Distinguish between malformed JSON syntax (400 Bad Request) and valid JSON failing field validation rules (422 Unprocessable Content).

100% Client-Side Privacy Guarantee

ToolZeno performs all HTTP status code searching, category filtering, multi-framework code generation, and comparisons locally inside your browser sandbox. No search queries or data are ever transmitted to external servers.

Frequently Asked Questions

HTTP status codes are standardized 3-digit numerical responses returned by web servers when a client (such as a web browser or mobile app) issues an HTTP request. They inform the client whether the request succeeded, requires a redirect, failed due to client error, or encountered a server crash.

HTTP status codes are divided into 5 distinct categories based on their first digit: 1xx Informational (request received), 2xx Success (action fulfilled), 3xx Redirection (further action needed), 4xx Client Error (bad request syntax or unauthorized), and 5xx Server Error (backend crash or gateway failure).

401 Unauthorized means the user is not authenticated—they are missing credentials (or their token expired) and must log in. 403 Forbidden means the user is authenticated, but their account role lacks permission to access that specific resource.

A 301 Moved Permanently redirect signals to search engine crawlers that a URL has moved forever, transferring 90-99% of link equity (ranking power) to the new destination. A 302 Found redirect indicates a temporary move, keeping the original URL indexed without transferring long-term ranking power.

No. The ToolZeno HTTP Status Code Lookup operates 100% client-side in your web browser. All search matching, status filtering, multi-framework code snippet generation, and comparisons execute locally in browser memory without sending data to any server.

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