Status Code Comparisons

HTTP 301 Moved Permanently vs 302 Found

Compare HTTP 301 Moved Permanently vs 302 Found. Learn when to use permanent vs temporary redirects for SEO, caching, and method preservation.

HTTP 301 Moved Permanently vs 308 Permanent Redirect

Compare HTTP 301 vs 308 permanent redirects. Learn how 308 preserves HTTP methods while 301 may rewrite POST to GET.

HTTP 302 Found vs 307 Temporary Redirect

Compare HTTP 302 Found vs 307 Temporary Redirect. Learn how 307 preserves HTTP methods while 302 may rewrite POST to GET.

HTTP 307 Temporary Redirect vs 308 Permanent Redirect

Compare HTTP 307 vs 308 redirects. Both preserve HTTP methods, but 307 is temporary and 308 is permanent. Learn when to use each.

HTTP 301 Moved Permanently vs 307 Temporary Redirect

Compare HTTP 301 vs 307 redirects. 301 is permanent (may change method), 307 is temporary (preserves method). Learn the right choice.

HTTP 401 Unauthorized vs 403 Forbidden

Compare HTTP 401 Unauthorized vs 403 Forbidden. 401 means missing credentials, 403 means insufficient permissions. Learn the difference.

HTTP 400 Bad Request vs 422 Unprocessable Content

Compare HTTP 400 Bad Request vs 422 Unprocessable Content. 400 is for malformed syntax, 422 for semantic validation errors.

HTTP 404 Not Found vs 410 Gone

Compare HTTP 404 Not Found vs 410 Gone. 404 is ambiguous, 410 means permanently removed. Learn SEO and caching implications.

HTTP 500 Internal Server Error vs 502 Bad Gateway

Compare HTTP 500 Internal Server Error vs 502 Bad Gateway. 500 is an app crash, 502 is a proxy-to-upstream failure.

HTTP 500 Internal Server Error vs 503 Service Unavailable

Compare HTTP 500 vs 503. 500 is an unexpected server error, 503 is a temporary condition with Retry-After. Learn when to use each.

HTTP 502 Bad Gateway vs 504 Gateway Timeout

Compare HTTP 502 Bad Gateway vs 504 Gateway Timeout. 502 means invalid upstream response, 504 means upstream timed out.

HTTP 200 OK vs 201 Created

Compare HTTP 200 OK vs 201 Created. 200 is general success, 201 means a resource was created. Learn proper REST API usage.

HTTP 200 OK vs 204 No Content

Compare HTTP 200 OK vs 204 No Content. 200 includes a response body, 204 signals success with no content. Learn proper API design.

HTTP 429 Too Many Requests vs 503 Service Unavailable

Compare HTTP 429 Too Many Requests vs 503 Service Unavailable. 429 is client rate limiting, 503 is server-wide downtime.

HTTP 404 Not Found vs gRPC 5 NOT_FOUND

Compare HTTP 404 Not Found vs gRPC NOT_FOUND. Same concept, different protocols. Learn how resource lookup errors differ across HTTP and gRPC.

HTTP 401 Unauthorized vs gRPC 16 UNAUTHENTICATED

Compare HTTP 401 Unauthorized vs gRPC UNAUTHENTICATED. Both mean missing credentials. Learn the naming confusion and gateway mapping.

HTTP 403 Forbidden vs gRPC 7 PERMISSION_DENIED

Compare HTTP 403 Forbidden vs gRPC PERMISSION_DENIED. Both mean authenticated but not authorized. Learn the cross-protocol mapping.

HTTP 500 Internal Server Error vs gRPC 13 INTERNAL

Compare HTTP 500 Internal Server Error vs gRPC INTERNAL. Both are catch-all server errors. Learn the cross-protocol equivalence.

HTTP 503 Service Unavailable vs gRPC 14 UNAVAILABLE

Compare HTTP 503 Service Unavailable vs gRPC UNAVAILABLE. Both signal temporary downtime. Learn retry strategies for each protocol.

HTTP 404 Not Found vs DNS NXDOMAIN (RCODE 3)

Compare HTTP 404 Not Found vs DNS NXDOMAIN. One is a missing URL path, the other is a missing domain. Learn the network layer difference.

HTTP 500 Internal Server Error vs WebSocket 1011 Internal Error

Compare HTTP 500 vs WebSocket 1011 Internal Error. Same meaning, different models: request-response vs persistent connection.

HTTP 401 Unauthorized vs SIP 401 Unauthorized

Compare HTTP 401 vs SIP 401 Unauthorized. Same code, different auth: Bearer tokens vs Digest nonces. Learn cross-protocol authentication.

HTTP 200 OK vs SIP 200 OK

Compare HTTP 200 OK vs SIP 200 OK. HTTP completes a request; SIP 200 starts a call session. Learn the protocol-specific semantics.

HTTP 200 OK vs gRPC 0 OK

Compare HTTP 200 OK vs gRPC 0 OK. gRPC OK is a trailer inside HTTP 200. Learn why HTTP status alone misses gRPC errors.

HTTP 408 Request Timeout vs gRPC 4 DEADLINE_EXCEEDED

Compare HTTP 408 Request Timeout vs gRPC DEADLINE_EXCEEDED. HTTP is server-side timeout, gRPC is client-set deadline. Learn the difference.

HTTP 409 Conflict vs gRPC 6 ALREADY_EXISTS

Compare HTTP 409 Conflict vs gRPC ALREADY_EXISTS. HTTP 409 covers all conflicts, gRPC is create-specific. Learn the mapping.

HTTP 429 Too Many Requests vs gRPC 8 RESOURCE_EXHAUSTED

Compare HTTP 429 Too Many Requests vs gRPC RESOURCE_EXHAUSTED. Both handle rate limiting, but gRPC is broader. Learn the mapping.

SIP 401 Unauthorized vs 407 Proxy Authentication Required

Compare SIP 401 vs 407. 401 is endpoint authentication, 407 is proxy authentication. Learn the SIP Digest auth challenge flow.

SIP 480 Temporarily Unavailable vs 486 Busy Here

Compare SIP 480 Temporarily Unavailable vs 486 Busy Here. 480 means unreachable, 486 means busy on a call. Learn the difference.

SIP 486 Busy Here vs 600 Busy Everywhere

Compare SIP 486 Busy Here vs 600 Busy Everywhere. 486 is one endpoint busy, 600 is all endpoints busy. Learn SIP call routing.

SIP 404 Not Found vs 604 Does Not Exist Anywhere

Compare SIP 404 Not Found vs 604 Does Not Exist Anywhere. 404 is local, 604 is a global definitive answer. Learn SIP routing logic.

SIP 488 Not Acceptable Here vs 606 Not Acceptable

Compare SIP 488 Not Acceptable Here vs 606 Not Acceptable. 488 is local, 606 is global. Learn SIP codec negotiation failures.

SIP 607 Unwanted vs 608 Rejected

Compare SIP 607 Unwanted vs 608 Rejected. 607 flags spam for network analytics, 608 is a neutral call decline. Learn the difference.

SMTP 450 Mailbox Unavailable vs 550 Mailbox Not Found

Compare SMTP 450 vs 550. 450 is temporary mailbox unavailability (retry), 550 is permanent (bounce). Learn email delivery handling.

SMTP 530 Authentication Required vs 535 Authentication Failed

Compare SMTP 530 vs 535. 530 means auth not attempted, 535 means auth failed. Learn SMTP authentication troubleshooting.

SMTP 421 Service Not Available vs 521 Host Does Not Accept Mail

Compare SMTP 421 vs 521. 421 is temporary server downtime, 521 means the host never accepts mail. Learn SMTP connection handling.

FTP 450 File Action Not Taken vs 550 File Unavailable

Compare FTP 450 vs 550. 450 is a temporary file lock, 550 means file not found or no permission. Learn FTP error handling.

FTP 227 Passive Mode vs 229 Extended Passive Mode

Compare FTP 227 Passive Mode vs 229 Extended Passive Mode. 227 is IPv4-only, 229 supports IPv6 and avoids NAT issues.

FTP 421 Service Not Available vs 530 Not Logged In

Compare FTP 421 vs 530. 421 means the server is unavailable, 530 means not authenticated. Learn FTP connection troubleshooting.

DNS SERVFAIL (RCODE 2) vs REFUSED (RCODE 5)

Compare DNS SERVFAIL vs REFUSED. SERVFAIL is a server error, REFUSED is a policy rejection. Learn DNS troubleshooting for each.

DNS NXDOMAIN (RCODE 3) vs NOERROR (RCODE 0)

Compare DNS NXDOMAIN vs NOERROR. NXDOMAIN means domain does not exist, NOERROR means it does. Learn DNS response interpretation.