HTTP Status Code Lookup
Developer UtilitiesQuick lookup tool for HTTP status codes — enter any status number and get the meaning, category, and usage guidelines instantly.. Free, private — all processing in your browser.
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The server has received the request headers and the client should proceed to send the request body.
1xx InformationalSwitching Protocols
The server is switching to a different protocol as requested by the client (e.g., upgrading to WebSocket).
1xx InformationalEarly Hints
Used to return some response headers before the final HTTP message, allowing preloading of resources.
1xx InformationalOK
The request succeeded. The meaning depends on the HTTP method: GET returns the resource, POST returns the result of the action.
2xx SuccessCreated
The request succeeded and a new resource was created. Typically returned after POST requests.
2xx SuccessAccepted
The request has been accepted for processing, but the processing has not been completed yet.
2xx SuccessNo Content
The request succeeded but there is no content to return. Common for DELETE requests.
2xx SuccessPartial Content
The server is returning only part of the resource due to a Range header sent by the client.
2xx SuccessMoved Permanently
The resource has permanently moved to a new URL. Search engines will update their index. Passes link equity.
3xx RedirectionFound
The resource is temporarily at a different URL. The client should continue using the original URL.
3xx RedirectionNot Modified
The resource has not been modified since the last request. The client should use its cached version.
3xx RedirectionTemporary Redirect
Like 302, but guarantees the HTTP method won't change. POST stays POST.
3xx RedirectionPermanent Redirect
Like 301, but guarantees the HTTP method won't change. The permanent version of 307.
3xx RedirectionBad Request
The server cannot process the request due to malformed syntax, invalid parameters, or missing required fields.
4xx Client ErrorUnauthorized
Authentication is required. The client must provide valid credentials. Despite the name, this means 'unauthenticated'.
4xx Client ErrorForbidden
The server understood the request but refuses to authorize it. The client does not have permission.
4xx Client ErrorNot Found
The server cannot find the requested resource. The most well-known HTTP error.
4xx Client ErrorMethod Not Allowed
The HTTP method is not supported for this endpoint. The response includes an Allow header listing valid methods.
4xx Client ErrorRequest Timeout
The server timed out waiting for the request. The client may retry.
4xx Client ErrorConflict
The request conflicts with the current state of the server. Common for duplicate entries.
4xx Client ErrorGone
The resource is permanently gone and will not be available again. Unlike 404, this is intentional.
4xx Client ErrorPayload Too Large
The request body is larger than the server is willing to accept.
4xx Client ErrorUnsupported Media Type
The server does not support the media type of the request body (e.g., wrong Content-Type).
4xx Client ErrorUnprocessable Entity
The request is well-formed but contains semantic errors. Common for validation failures.
4xx Client ErrorToo Many Requests
Rate limiting — the client has sent too many requests in a given time period.
4xx Client ErrorInternal Server Error
A generic server error. Something went wrong on the server side.
5xx Server ErrorBad Gateway
The server, acting as a gateway, received an invalid response from an upstream server.
5xx Server ErrorService Unavailable
The server is temporarily unable to handle the request due to maintenance or overload.
5xx Server ErrorGateway Timeout
The server, acting as a gateway, didn't receive a timely response from the upstream server.
5xx Server ErrorThe HTTP Status Lookup gives you the meaning of any HTTP status code instantly. Type a three-digit number (200, 404, 502, 418), get back the official name, category, description, when to use or expect it, and related codes. This is the fastest way to answer \"what does 422 actually mean?\" or \"why am I seeing 504?\" when debugging an API or reading server logs. Unlike the comprehensive HTTP Status Codes reference, this tool is optimized for quick lookup — type, read, move on.
Works for every registered code from 100 to 511 plus common non-standard codes used by specific vendors (Cloudflare 520-527 error codes, nginx 494, etc.). Search by number or by keyword (typing \"auth\" finds 401 and 403; \"redirect\" finds 301, 302, 303, 307, 308). Each result shows category (1xx informational through 5xx server error), description, common causes, and fix suggestions when applicable. Designed for the moment mid-debug when you just need the one piece of information about one code.
HTTP Status Code Lookup — key features
Instant lookup
Type a status code number and see the meaning immediately with no navigation.
Keyword search
Search by concept ("auth", "rate limit", "redirect") to find relevant codes by use case.
Standard + vendor codes
Covers IANA-registered codes plus commonly used vendor codes (Cloudflare, nginx, Microsoft).
Cause and fix guidance
For error codes, suggests common causes and how to handle them in client code or server operations.
Related codes
Each lookup shows related codes for quick comparison (401 links to 403, 301 links to 302 and 307).
RFC references
Each code links to the authoritative RFC section for deep reading when needed.
Category browse
Quick filters by 1xx, 2xx, 3xx, 4xx, 5xx for browsing all codes in a category.
Client-side only
All lookup runs in your browser with no network calls; fast even offline after initial load.
How to use the HTTP Status Code Lookup
- 1
Type a status code
Enter 404, 500, 302, or any three-digit status code in the search field.
- 2
Or search by keyword
Type "auth", "redirect", "timeout" to find codes by concept.
- 3
Read the result
See the name, category, description, causes, and fix guidance for the code.
- 4
Check related codes
Related cross-references help you compare similar codes (400 vs 422, 401 vs 403).
- 5
Follow RFC link if needed
For authoritative details, click through to the relevant RFC section.
Common use cases for the HTTP Status Code Lookup
API development
- →Picking the right code: Mid-design, quickly check which code is appropriate for a given error condition.
- →Reviewing responses: Look up unfamiliar codes in API responses during integration work.
- →Documentation drafting: Quickly confirm the exact official name of a status code when writing API docs.
Debugging and ops
- →Log investigation: Unfamiliar status codes appearing in logs (522, 494) — look them up quickly to diagnose the issue.
- →Monitoring alerts: Understand alert payloads referencing specific status codes at 2 AM.
- →Support ticket triage: Customer reports "I get a 502" — look up what it means before responding.
Learning
- →Developer onboarding: New team members use the lookup to quickly learn the status code landscape.
- →Interview prep: Refresh knowledge of HTTP semantics before a backend interview.
- →Teaching: Instructors point to the lookup as a reference for students learning REST.
HTTP Status Code Lookup — examples
404 lookup
Classic not-found error.
404
name: Not Found category: 4xx Client Error meaning: the server cannot find the requested resource causes: invalid URL, resource deleted, typo in path fix: verify URL, check API docs for correct path
422 lookup
Less common but important API code.
422
name: Unprocessable Content category: 4xx Client Error meaning: request is syntactically valid but semantically wrong typical use: validation errors on otherwise valid requests related: 400 (malformed), 409 (conflict)
Keyword search
Finding all auth-related codes.
auth
401 Unauthorized — authentication required 403 Forbidden — authenticated but not allowed 407 Proxy Authentication Required 511 Network Authentication Required
Cloudflare code
522
name: Connection Timed Out (Cloudflare) not IANA-registered — Cloudflare-specific meaning: Cloudflare could not establish TCP connection to origin fix: check origin server is reachable, firewall not blocking Cloudflare IPs
Concept search
Finding codes for rate limiting.
rate limit
429 Too Many Requests — client exceeded rate limit (typically includes Retry-After header)
Technical details
Status code lookup is essentially a key-value store against the IANA registry (60+ standard codes) plus common vendor extensions.
Implementation: a JSON dictionary mapping code number to { name, category, description, fix, references }. Lookup is O(1); keyword search is a linear scan with relevance scoring.
The canonical source is the IANA HTTP Status Code Registry (https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml). Non-registered codes used in the wild:
- 418 I\u2019m a Teapot (RFC 2324 April Fools\u2019 joke, not IANA registered)
- 419 Page Expired (Laravel)
- 420 Enhance Your Calm (Twitter, deprecated)
- 440 Login Time-out (Microsoft IIS)
- 444 No Response (nginx)
- 494 Request Header Too Large (nginx)
- 495-499 (nginx specific SSL codes)
- 520-527 (Cloudflare)
- 598-599 (network timeout errors, unregistered)
The tool includes these with clear labels that they are vendor-specific, not IANA-registered.
Fuzzy search: typing \"auth\" matches 401 (Unauthorized) and 403 (Forbidden). \"rate\" matches 429 (Too Many Requests). \"timeout\" matches 408 (Request Timeout) and 504 (Gateway Timeout). Relevance scoring weighs exact name matches highest, then description matches, then category matches.
For each code, the result includes:
- Code number and name
- Category (1xx-5xx with plain name)
- RFC reference and URL
- Description in plain English
- When it occurs (causes)
- How to handle (for client code) or fix (for server code)
- Related codes with brief differentiators
For 4xx codes, a common cause list helps debugging; for 5xx codes, an escalation guide helps operators decide next steps.
Common problems and solutions
⚠Vendor-specific code assumed standard
Codes like 520-527 (Cloudflare) and 494 (nginx) are not IANA-registered. Other systems may interpret them differently. The tool labels these clearly — don’t assume a client handles them.
⚠Misinterpreting 5xx as client fault
5xx codes indicate a server-side problem, not client error. Users seeing 500 are not doing anything wrong; the server needs fixing. Don’t blame the client for 5xx codes.
⚠Using 200 with error details
Returning 200 OK with an error body confuses clients that rely on status codes for flow control. Use appropriate 4xx or 5xx. GraphQL is the only context where 200-with-errors is conventional.
⚠Missing Retry-After on 429 and 503
Clients should retry 429 and 503 responses, but without Retry-After they may retry immediately and overload the server. Always include it when returning these codes.
⚠Unregistered custom codes
Using a code like 666 or 777 is not allowed — clients may ignore or treat it undefined-ly. Pick a registered code and use the body for details.
⚠Confusing 502 and 504
502 means upstream responded with invalid response; 504 means upstream did not respond in time. Different root causes, different fixes. The distinction matters when debugging gateway errors.
⚠Treating 3xx as errors
3xx codes are redirections — normal behavior, not errors. Your client should follow the Location header or respect 304 caching. Monitoring that flags all 3xx as errors will produce false positives.
HTTP Status Code Lookup — comparisons and alternatives
Compared to Google \"what is HTTP 404\", this tool returns the canonical answer immediately with additional context (causes, fix, related codes). Google takes you to a random blog; this tool to the authoritative answer.
Compared to the IANA registry, this tool is much more readable and includes practical guidance. IANA is the authoritative source; this is the practical reference.
Compared to the comprehensive HTTP Status Codes tool in this suite, this one is optimized for quick lookup while the comprehensive reference is for learning the full landscape. Use this when debugging; use the reference when learning.
Frequently asked questions about the HTTP Status Code Lookup
▶How do I look up an HTTP status code?
Type the three-digit number (like 404 or 503) into the search field and the meaning appears instantly. You can also search by keyword — typing "rate limit" finds 429, "redirect" finds 301-308, "auth" finds 401 and 403.
▶What does HTTP 500 mean?
500 Internal Server Error is a generic 5xx server error. The server encountered a problem it could not handle. It is a catch-all when no more specific 5xx applies. As a client, you can’t fix a 500 — the server needs debugging.
▶Is 302 or 301 better for redirects?
Depends on permanence. 301 Moved Permanently tells browsers and search engines to update the link — use for permanent moves. 302 Found is temporary. Misuse of 302 where 301 is intended hurts SEO because engines keep the old URL.
▶What is the difference between 401 and 403?
401 Unauthorized means the client must authenticate (present credentials). 403 Forbidden means the authenticated client is not allowed, even with valid credentials. 401 says "who are you?"; 403 says "you\u2019re not allowed here".
▶Does this tool cover Cloudflare and nginx codes?
Yes. Vendor-specific codes (Cloudflare 520-527, nginx 444 and 494) are included with clear labels noting they are non-standard. This helps debugging when you see them in logs or responses but they are not in the IANA registry.
▶What is a 418?
I’m a Teapot — an RFC 2324 April Fools’ joke code (Hyper Text Coffee Pot Control Protocol). Not for real use. Some APIs return it as an Easter egg but it has no functional meaning.
▶Can I search by keyword?
Yes. Type a concept like "timeout", "validation", "server error", "auth" and the tool returns all status codes matching that concept. Useful when you know what you want but not the specific number.
▶Is the lookup up to date with RFC 9110?
Yes. The tool uses RFC 9110 (current HTTP semantics standard, 2022) and the latest IANA registry. RFC 9110 largely preserves the status code definitions from RFC 7231 with minor clarifications.
Additional resources
- IANA HTTP Status Code Registry — Official registry of all assigned HTTP status codes.
- RFC 9110 HTTP Semantics — Current authoritative specification for HTTP.
- MDN HTTP Status — Detailed MDN reference with browser-compatibility notes.
- Cloudflare status codes — Cloudflare-specific codes (520-527) reference.
- nginx error codes — nginx-specific status codes and their meanings.
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