What is the difference between 401 and 403?

401 Unauthorized means the user is not authenticated (login required). 403 Forbidden means authenticated but lacking permission (access denied). 401 must include a WWW-Authenticate header.

302 vs 307 vs 308 — what is the difference?

302 Found: temporary redirect, method may change to GET. 307 Temporary Redirect: temporary, method preserved. 308 Permanent Redirect: permanent (replaces 301), method preserved. Use 301/308 for SEO, 307 for preserving POST in APIs.

Which status codes should REST APIs use?

Create: 201, Retrieve success: 200, Delete (no content): 204, Validation failure: 422 or 400, Not authenticated: 401, No permission: 403, Not found: 404, Conflict/duplicate: 409, Server error: 500.

How to handle 429 Too Many Requests?

The server should include a Retry-After header indicating when to retry. Clients should implement exponential backoff and reduce request rate when 429 repeats.

200HTTP Status Codes

Look up HTTP status codes and their meanings

100

Continue

서버가 요청 헤더를 받았으며, 클라이언트가 본문을 전송해야 함

101

Switching Protocols

서버가 프로토콜 전환을 수락

200

요청이 성공적으로 처리됨

201

Created

요청이 성공하여 새 리소스가 생성됨

204

No Content

요청이 성공했지만 반환할 콘텐츠 없음

301

Moved Permanently

리소스가 영구적으로 이동됨

302

Found

리소스가 임시로 이동됨

304

Not Modified

캐시된 버전 사용 가능

400

Bad Request

잘못된 요청 구문 또는 유효하지 않은 매개변수

401

Unauthorized

인증이 필요함 (로그인 필요)

403

Forbidden

서버가 요청을 거부 (권한 없음)

404

Not Found

요청한 리소스를 찾을 수 없음

405

Method Not Allowed

요청 메서드가 허용되지 않음

408

Request Timeout

서버가 요청 대기 시간 초과

409

Conflict

요청이 현재 서버 상태와 충돌

413

Payload Too Large

요청 본문이 너무 큼

422

Unprocessable Entity

요청은 잘 만들어졌으나 처리할 수 없음

429

Too Many Requests

너무 많은 요청 (Rate Limiting)

500

Internal Server Error

서버 내부 오류

502

Bad Gateway

게이트웨이/프록시 서버가 잘못된 응답 수신

503

Service Unavailable

서버가 일시적으로 요청 처리 불가 (과부하/유지보수)

504

Gateway Timeout

게이트웨이/프록시 서버가 응답 대기 시간 초과

HTTP Status Codes: Complete Reference

HTTP status codes are 3-digit numbers returned by a server in response to a client request. They are essential knowledge for web development, API design, and server debugging. The five ranges are: 1xx (informational), 2xx (success), 3xx (redirection), 4xx (client error), 5xx (server error).

Overview of All Five Ranges

1xx Informational: Request received, processing in progress (100 Continue, 101 Switching Protocols)
2xx Success: Request processed successfully (200 OK, 201 Created, 204 No Content)
3xx Redirection: Further action needed (301, 302, 304, 307, 308)
4xx Client Error: Problem with the request (400, 401, 403, 404, 429)
5xx Server Error: Server failed a valid request (500, 502, 503, 504)

Commonly Confused Codes

Code	Name	Key Distinction
401	Unauthorized	Not authenticated (login required)
403	Forbidden	Authenticated but lacks permission
302	Found	Temporary redirect, method may change
307	Temporary Redirect	Temporary, method preserved
308	Permanent Redirect	Permanent (replaces 301), method preserved
400	Bad Request	Syntax error, malformed request
422	Unprocessable Entity	Well-formed but semantically invalid (validation failure)

Choosing the Right Code for REST APIs

Resource created → 201 Created + Location header
Delete with no body → 204 No Content
Validation failure → 422 Unprocessable Entity (422 preferred, 400 acceptable)
Rate limit hit → 429 Too Many Requests + Retry-After header
Scheduled maintenance → 503 Service Unavailable + Retry-After header

How to Use

Type a status code (e.g. 404) or keyword (e.g. timeout) in the search box.
Use color-coded categories to instantly grasp the nature of each code.

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