Understand everysoftware error code.

BROWSE BY PROTOCOL & PLATFORM

100 / 100 records

Search⌘ KFrequencyLevelRows per page

All categories

Meaning	Category	Level	Frequency	English name / Aliases	Protocol / Platform	Source	Related codes	Troubleshooting	Context
Bad Request	HTTP 4xx	Basic	Common	Bad Request; HTTP 400	`HTTP`	Official docs ↗	415 · 422	Validate the request body, parameter types, and Content-Type.	Browsers, REST APIs, reverse proxies
Unauthorized	HTTP 4xx	Basic	Common	Unauthorized; HTTP 401	`HTTP`	Official docs ↗	403 · 16 UNAUTHENTICATED	Check missing or expired credentials and authenticate again.	Browsers, REST APIs, reverse proxies
Payment Required	HTTP 4xx	Advanced	Specialized	Payment Required; HTTP 402	`HTTP`	Official docs ↗	—	Check the API documentation for implementation-specific meaning.	Browsers, REST APIs, reverse proxies
Forbidden	HTTP 4xx	Basic	Common	Forbidden; HTTP 403	`HTTP`	Official docs ↗	401 · 7 PERMISSION_DENIED	Check permissions, access policies, and resource ownership.	Browsers, REST APIs, reverse proxies
Not Found	HTTP 4xx	Basic	Common	Not Found; HTTP 404	`HTTP`	Official docs ↗	410 · 5 NOT_FOUND	Check the route, resource identifier, and deployment path.	Browsers, REST APIs, reverse proxies
Method Not Allowed	HTTP 4xx	Basic	Common	Method Not Allowed; HTTP 405	`HTTP`	Official docs ↗	—	Check the HTTP method and the Allow response header.	Browsers, REST APIs, reverse proxies
Not Acceptable	HTTP 4xx	Basic	Common	Not Acceptable; HTTP 406	`HTTP`	Official docs ↗	—	Check Accept and other content negotiation headers.	Browsers, REST APIs, reverse proxies
Proxy Authentication Required	HTTP 4xx	Advanced	Specialized	Proxy Authentication Required; HTTP 407	`HTTP`	Official docs ↗	—	Check proxy credentials and configuration.	Browsers, REST APIs, reverse proxies
Request Timeout	HTTP 4xx	Basic	Common	Request Timeout; HTTP 408	`HTTP`	Official docs ↗	504 · ETIMEDOUT	Check network and upload timing; confirm retry safety.	Browsers, REST APIs, reverse proxies
Conflict	HTTP 4xx	Basic	Common	Conflict; HTTP 409	`HTTP`	Official docs ↗	412 · 10 ABORTED	Check versions, duplicates, and concurrent updates.	Browsers, REST APIs, reverse proxies
Gone	HTTP 4xx	Basic	Common	Gone; HTTP 410	`HTTP`	Official docs ↗	404	Update the resource URL or remove obsolete references.	Browsers, REST APIs, reverse proxies
Length Required	HTTP 4xx	Advanced	Specialized	Length Required; HTTP 411	`HTTP`	Official docs ↗	—	Check Content-Length and request transfer framing.	Browsers, REST APIs, reverse proxies
Precondition Failed	HTTP 4xx	Basic	Common	Precondition Failed; HTTP 412	`HTTP`	Official docs ↗	409 · 428	Check ETag, If-Match, and other preconditions.	Browsers, REST APIs, reverse proxies
Content Too Large	HTTP 4xx	Basic	Common	Content Too Large; HTTP 413; Payload Too Large; Request Entity Too Large	`HTTP`	Official docs ↗	1009	Check upload size and gateway or application limits.	Browsers, REST APIs, reverse proxies
URI Too Long	HTTP 4xx	Basic	Common	URI Too Long; HTTP 414	`HTTP`	Official docs ↗	—	Reduce query parameters and follow the API contract.	Browsers, REST APIs, reverse proxies
Unsupported Media Type	HTTP 4xx	Basic	Common	Unsupported Media Type; HTTP 415	`HTTP`	Official docs ↗	400 · 422	Check Content-Type, Content-Encoding, and the payload.	Browsers, REST APIs, reverse proxies
Range Not Satisfiable	HTTP 4xx	Advanced	Specialized	Range Not Satisfiable; HTTP 416	`HTTP`	Official docs ↗	—	Check Range against the resource length.	Browsers, REST APIs, reverse proxies
Expectation Failed	HTTP 4xx	Advanced	Specialized	Expectation Failed; HTTP 417	`HTTP`	Official docs ↗	—	Check Expect and intermediary support.	Browsers, REST APIs, reverse proxies
Misdirected Request	HTTP 4xx	Advanced	Specialized	Misdirected Request; HTTP 421	`HTTP`	Official docs ↗	—	Check host routing, TLS, and connection reuse.	Browsers, REST APIs, reverse proxies
Unprocessable Content	HTTP 4xx	Basic	Common	Unprocessable Content; HTTP 422; Unprocessable Entity	`HTTP`	Official docs ↗	400 · 3 INVALID_ARGUMENT	Check field constraints and validation errors.	Browsers, REST APIs, reverse proxies

ℹ

QUICK TIP

Click any error code to copy

Interpret codes within their protocol and platform. HTTP statuses, WebSocket close codes, and exception names use different namespaces. 1000 is normal closure; 1005, 1006, and 1015 must not be sent. Check idempotency before retrying writes.

Understand every
software error code.

Browse by protocol & platform

No matching error codes

Click any error code to copy

References & further reading