Every HTTP status code explained in plain English, with causes, fixes, SEO impact, and monitoring tips. Filter, search, and look up any code instantly.
The codes you’ll encounter most often. Click any card for full details.
HTTP status codes are grouped into five classes. The first digit tells you the general type of response at a glance.
Request received, process continuing. Rarely seen by end users. These are interim responses.
The request was successfully received, understood, and accepted. Everything worked.
Further action is needed. The resource has moved or additional steps are required.
The request contains bad syntax or cannot be fulfilled, a client-side issue.
The server failed to fulfil a valid request. These need immediate attention.
All 34 codes in plain English, with what usually causes each one and what to do about it.
The server has received the request headers and the client should proceed to send the request body.
Common causes: Large file uploads; Expectation header in request.
How to fix: No action needed: this is normal interim behaviour.
SEO impact: Neutral: not typically seen by crawlers. User impact: Transparent: handled automatically.
Monitoring: Not typically monitored as it's an interim response.
The server is changing protocols (e.g. upgrading from HTTP to WebSocket).
Common causes: WebSocket upgrade requests; Protocol upgrade negotiations.
How to fix: No action needed if intentional upgrade.
SEO impact: Neutral: not relevant to SEO. User impact: Transparent: enables real-time features.
Monitoring: Monitor WebSocket connections if using real-time features.
The server has received the request and is processing it, but no response is available yet.
Common causes: Long-running WebDAV requests; Complex server-side operations.
How to fix: No action needed: indicates processing is underway.
SEO impact: Neutral. User impact: Transparent.
Monitoring: Rare: indicates long-running operations.
Hints to the browser to start preloading resources while the server is still preparing the main response.
Common causes: HTTP/2 performance optimisations; Server-side render pipelines.
How to fix: No action needed: this is a performance feature.
SEO impact: Positive: can improve page load speed. User impact: Positive: faster perceived load times.
Monitoring: Can be used to speed up first contentful paint.
Everything worked perfectly. The server returned the requested data.
Common causes: Successful GET request; Page loaded normally; API call succeeded.
How to fix: No action needed: this is the desired response.
SEO impact: Positive: search engines can crawl and index the page normally. User impact: Perfect: users see the content they requested.
Monitoring: Monitor to ensure pages consistently return 200.
The request succeeded and a new resource was created (typically after POST).
Common causes: Successful form submission; New database record created; File upload completed.
How to fix: No action needed: indicates successful creation.
SEO impact: Neutral: typically for API/form responses. User impact: Positive: user's action was successful.
Monitoring: Track creation endpoints to ensure they're working.
The request was accepted for processing, but the processing hasn't been completed yet.
Common causes: Async operations (background jobs); Queued tasks; Batch processing.
How to fix: No action needed: indicates async processing.
SEO impact: Neutral. User impact: Depends on implementation: often shows a "pending" state.
Monitoring: Ensure async jobs actually complete and check job queues.
The request was successful but there's nothing to send back (often for DELETE).
Common causes: Successful DELETE request; Action completed with no response data needed.
How to fix: No action needed: this is intentional.
SEO impact: Neutral: not used for crawlable pages. User impact: Depends: users may see a confirmation message.
Monitoring: Monitor DELETE/PATCH endpoints for 204 responses.
The server is delivering only part of the resource because the client requested a specific range.
Common causes: Video streaming with range requests; Resumable downloads; Chunked transfers.
How to fix: No action needed: this is correct for range requests.
SEO impact: Neutral. User impact: Positive: enables smooth video/audio streaming.
Monitoring: Expected for media streaming, but monitor for errors if streaming breaks.
The page has permanently moved to a new address. Browsers and search engines should use the new URL.
Common causes: Site restructuring; Domain change; URL cleanup; Content consolidation.
How to fix: Update internal links to new URL; Ensure redirect is correct; Update sitemap.
SEO impact: Important: passes link equity, search engines update index. User impact: Transparent: users are automatically redirected.
Monitoring: Monitor redirect chains to avoid multiple hops.
The page is temporarily at a different address but may return to the original URL.
Common causes: A/B testing; Maintenance redirects; Temporary promotions.
How to fix: Use 301 if the move is permanent; Remove when no longer temporary.
SEO impact: Caution: doesn't pass full link equity if used long-term. User impact: Transparent: users are redirected automatically.
Monitoring: Track 302s to ensure they're actually temporary.
The page hasn't changed since you last visited, so use your cached version.
Common causes: Browser cache validation; Conditional GET requests; ETags matching.
How to fix: No action needed: improves performance.
SEO impact: Positive: efficient crawling. User impact: Positive: faster page loads from cache.
Monitoring: Good for performance: indicates proper caching.
Temporarily redirect to another URL, keeping the same HTTP method (POST stays POST).
Common causes: Temporary URL changes; Load balancing; Maintenance mode.
How to fix: Use 301/308 if permanent.
SEO impact: Similar to 302, so use sparingly. User impact: Transparent: request is redirected.
Monitoring: Monitor for redirect loops.
Permanently redirected, and the HTTP method stays the same (POST stays POST).
Common causes: Permanent URL changes for POST endpoints; API endpoint migrations.
How to fix: Update API clients to use new URL; Document the change.
SEO impact: Similar to 301: passes link equity. User impact: Transparent: automatically redirected.
Monitoring: Ensure redirect target is stable.
The request was malformed or contains invalid syntax the server can't understand.
Common causes: Invalid JSON/XML in request body; Malformed URL parameters; Missing required fields; Invalid characters in URL.
How to fix: Check request syntax and formatting; Validate input data; Review API documentation; Check for special characters in URLs.
SEO impact: Negative: search engines can't access the content. User impact: Poor: users see an error and can't access content.
Monitoring: Track 400 errors to identify form/API issues.
You need to log in or provide valid credentials to access this resource.
Common causes: Missing login credentials; Invalid username/password; Expired session token; Missing API key.
How to fix: Log in with valid credentials; Check authentication headers; Refresh expired tokens; Verify API key is correct.
SEO impact: Neutral: expected for protected content. User impact: Expected for login-protected pages.
Monitoring: Monitor authentication endpoints for unexpected failures.
You're authenticated, but you don't have permission to access this resource.
Common causes: Insufficient permissions; IP address blocked; Country/region restrictions; File permissions too restrictive.
How to fix: Check user permissions; Verify IP whitelist/blacklist; Review file/directory permissions; Check WAF rules.
SEO impact: Negative: content is inaccessible to search engines. User impact: Frustrating: users know the page exists but can't access it.
Monitoring: Monitor for unexpected 403s that block legitimate users.
The page or resource you're looking for doesn't exist on this server.
Common causes: URL typed incorrectly; Page deleted or moved without redirect; Broken internal/external links; Missing file or resource.
How to fix: Check URL spelling and capitalisation; Create 301 redirect from old URL; Fix broken internal links; Create a helpful custom 404 page.
SEO impact: Negative: broken pages hurt rankings and link equity. User impact: Frustrating: users hit dead ends and may leave.
Monitoring: Track 404 errors to catch broken links and deleted pages.
You're using the wrong HTTP method (e.g. POST instead of GET) for this URL.
Common causes: Form submitted with wrong method; API called with incorrect HTTP verb; Server configuration restricts methods.
How to fix: Check API documentation for the correct method; Update form method attribute; Verify server allows the HTTP method.
SEO impact: Neutral: typically affects forms/APIs. User impact: Poor: forms/actions fail unexpectedly.
Monitoring: Monitor API endpoints for method errors.
The server didn't receive the complete request within the allowed time.
Common causes: Slow network connection; Large file upload interrupted; Client took too long to send request.
How to fix: Increase server timeout settings; Optimise network connection; Break large uploads into smaller chunks.
SEO impact: Neutral: uncommon for search crawlers. User impact: Poor: users may need to retry.
Monitoring: Monitor timeout rates to identify performance issues.
The request couldn't be completed because it conflicts with the current state of the resource.
Common causes: Concurrent edits to same resource; Duplicate resource creation attempt; Version conflict in API.
How to fix: Implement optimistic locking; Retry with updated resource state; Add conflict resolution logic.
SEO impact: Neutral: typically API-only. User impact: Moderate: needs clear user messaging about the conflict.
Monitoring: Monitor APIs for unexpected 409s indicating concurrency issues.
The resource used to exist but has been permanently removed with no forwarding address.
Common causes: Content permanently deleted; Expired promotional pages; Discontinued products.
How to fix: Return 410 for intentionally removed content; Provide helpful message about alternatives; Use 301 if there's a replacement.
SEO impact: Better than 404: tells search engines to remove from index faster. User impact: Clear: users know content is gone, not broken.
Monitoring: Use 410 instead of 404 for intentionally removed content.
This is a joke status from an April Fools' RFC. The server refuses to brew coffee because it's a teapot.
Common causes: Intentional Easter egg; HTCPCP (Hyper Text Coffee Pot Control Protocol) implementation.
How to fix: No fix needed. This is humour. Remove if used incorrectly in production.
SEO impact: Should not be used in production. User impact: Confusing if encountered unexpectedly.
Monitoring: Should never appear in production monitoring.
The server understands the request format but can't process the semantic instructions.
Common causes: Validation errors in API payload; Business logic violations; Invalid field values that pass syntax checks.
How to fix: Check validation rules; Review API documentation for required fields; Return clear error messages to clients.
SEO impact: Neutral: API only. User impact: Poor if not clearly communicated to the user.
Monitoring: Monitor for 422s on form submission endpoints.
You've sent too many requests in a given time period. Slow down and try again later.
Common causes: API rate limit exceeded; Too many login attempts; Aggressive crawling/scraping; DDoS protection triggered.
How to fix: Implement exponential backoff; Respect Retry-After header; Reduce request frequency; Authenticate for higher rate limits.
SEO impact: Can affect crawling, so ensure search engines aren't rate-limited. User impact: Frustrating: users may need to wait before retrying.
Monitoring: Monitor rate limiting to ensure legitimate users aren't blocked.
This content has been removed due to legal demands (copyright, government order, etc.).
Common causes: DMCA takedown; Court order; Government censorship; Geographic restrictions.
How to fix: Comply with legal requirements; Document the legal basis; Provide explanation to users.
SEO impact: Negative: content is unavailable. User impact: Clear: users understand why content is blocked.
Monitoring: Track legal takedowns for compliance reporting.
Something went wrong on the server but it's not sure what. This is the generic catch-all server error.
Common causes: Unhandled exception in code; Server misconfiguration; Database connection failure; Syntax errors in code; Resource exhaustion.
How to fix: Check server error logs; Review recent code changes; Test database connectivity; Check file permissions; Verify server memory/CPU; Check .htaccess syntax.
SEO impact: Very negative: search engines may deindex pages with persistent 500s. User impact: Very poor: users can't access content, site appears broken.
Monitoring: Critical: set up immediate alerts for 500 errors.
The server doesn't know how to fulfil the request. The method may not be implemented.
Common causes: Unsupported HTTP method; Unimplemented feature; Server software too old.
How to fix: Check if the HTTP method is supported; Update server software; Implement the required functionality.
SEO impact: Negative if persistent. User impact: Poor.
Monitoring: Rare: indicates missing server features.
A gateway/proxy received an invalid response from another server it tried to contact.
Common causes: Backend server down; Proxy can't reach backend; Backend crashed; Network connectivity issues; Backend overloaded.
How to fix: Restart backend servers; Check backend server health; Verify network connectivity; Check firewall rules; Review load balancer config.
SEO impact: Very negative: if persistent, pages may be deindexed. User impact: Very poor: site appears completely down.
Monitoring: Critical: indicates infrastructure issues needing immediate attention.
The server is temporarily unable to handle the request, usually due to maintenance or overload.
Common causes: Scheduled maintenance; Server overloaded; Too many concurrent connections; Database unavailable.
How to fix: Wait for maintenance to complete; Scale up server resources; Optimise slow queries; Implement caching; Use Retry-After header.
SEO impact: Moderate: use with Retry-After header during planned maintenance. User impact: Moderate if temporary: users can retry later.
Monitoring: Monitor for unexpected 503s indicating capacity issues.
A gateway didn't receive a timely response from the upstream server it tried to contact.
Common causes: Backend processing too slow; Database query timeout; Backend server unresponsive; Network latency.
How to fix: Optimise slow backend processes; Increase gateway timeout; Add caching layer; Scale backend resources; Optimise database queries.
SEO impact: Negative: slow response times hurt rankings. User impact: Poor: long wait followed by error.
Monitoring: Monitor response times and alert on timeout spikes.
The server doesn't support the HTTP protocol version used in the request.
Common causes: Outdated server software; Client using too-new HTTP version; Server configuration issue.
How to fix: Update server software; Configure server to support HTTP/2 or HTTP/3; Check client HTTP version compatibility.
SEO impact: Rare: most crawlers use standard HTTP versions. User impact: Rare: most browsers fall back gracefully.
Monitoring: Should be very rare: it indicates a configuration issue.
The server doesn't have enough storage space to process the request.
Common causes: Disk full on server; Storage quota exceeded; WebDAV storage limit reached.
How to fix: Free up disk space; Increase storage quota; Implement data archival; Add storage capacity.
SEO impact: Very negative if persistent. User impact: Poor: uploads and operations fail.
Monitoring: Monitor disk usage and alert before storage runs out.
The server detected an infinite loop while processing the request.
Common causes: Circular resource references in WebDAV; Redirect loops; Recursive processing.
How to fix: Fix circular references; Check for redirect loops; Review recursive operations.
SEO impact: Negative if it affects crawlable pages. User impact: Poor.
Monitoring: Monitor for redirect chains that might create loops.
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