100
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The server has received request headers and the client should proceed to send the body.
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Visual API cheat sheet
HTTP Status Code Cheat Sheet
Learn API response codes with examples, tester notes, common mistakes, and interview-friendly explanations.
For DevelopersFor TestersFor StudentsREST API Friendly
request.http
GET /api/users/123
— — —
Status: 200 OK
Response received successfully
{
"id": 123,
"name": "Ada Lovelace",
"role": "engineer"
}Explore
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Search by code, name, or keyword. Filter by category to focus on what matters.
1xx Informational
101
Switching Protocols
The server agrees to switch protocols as requested by the client.
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200
OK
The request succeeded and the response contains the requested resource.
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201
Created
The request was successful and a new resource was created.
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202
Accepted
The request was accepted for processing but has not completed yet.
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204
No Content
The request succeeded and there is no content to return.
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301
Moved Permanently
The resource has been permanently moved to a new URL.
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302
Found
The resource is temporarily located at a different URL.
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304
Not Modified
Cached version is still valid — no body is returned.
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400
Bad Request
The server cannot process the request due to malformed syntax or invalid input.
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401
Unauthorized
Authentication is required and has failed or has not been provided.
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403
Forbidden
The user is authenticated but does not have permission to access the resource.
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404
Not Found
The requested resource does not exist on the server.
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405
Method Not Allowed
The HTTP method is not supported for this resource.
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408
Request Timeout
The client did not send a complete request in the time the server was prepared to wait.
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409
Conflict
The request conflicts with the current state of the resource.
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415
Unsupported Media Type
The request payload format is not supported by the server.
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422
Unprocessable Content
The request was well-formed but contains semantic validation errors.
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429
Too Many Requests
The client has sent too many requests in a given amount of time.
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500
Internal Server Error
The server encountered an unexpected condition that prevented it from fulfilling the request.
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501
Not Implemented
The server does not support the functionality required to fulfill the request.
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502
Bad Gateway
The server, acting as a gateway or proxy, received an invalid response from upstream.
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503
Service Unavailable
The server is temporarily unable to handle the request, often due to overload or maintenance.
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504
Gateway Timeout
The gateway did not receive a timely response from the upstream server.
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Compare
Common Confusions Explained
Side-by-side breakdowns of the status codes developers most often mix up.
200 OK vs 201 Created
200 OK
The request succeeded. Use for successful GET, PUT, PATCH responses with a body.
201 Created
The request succeeded and a new resource was created. Use for successful POST that creates a resource.
401 Unauthorized vs 403 Forbidden
401 Unauthorized
The request lacks valid authentication. Token missing, expired, or invalid.
403 Forbidden
Authentication worked but the user is not allowed to access this resource.
400 Bad Request vs 422 Unprocessable
400 Bad Request
Malformed request — bad JSON, missing required fields, wrong types.
422 Unprocessable Content
Well-formed request but semantic validation failed, e.g. invalid email format.
404 Not Found vs 410 Gone
404 Not Found
Resource does not exist or never did. Default for missing items.
410 Gone
Resource used to exist but has been intentionally removed and will not return.
500 Internal Server Error vs 503 Service Unavailable
500 Internal Server Error
Unexpected server-side failure. Indicates a bug or unhandled exception.
503 Service Unavailable
Server is temporarily unable to respond — overload, maintenance, or upstream outage.
For Testers
What Should You Validate?
Real API scenarios mapped to the status codes you should assert against.
Login API
- 200Successful login with valid credentials
- 400Missing required fields
- 401Invalid credentials
- 429Too many login attempts
- 500Unexpected server failure
Create User API
- 201User created successfully
- 400Invalid payload
- 409Duplicate email or username
- 422Validation errors
- 500Server failure
File Upload API
- 200Successful upload (returning body)
- 201Successful upload — new file resource
- 400Missing file
- 415Unsupported file type
- 500Server failure
Payment API
- 200Payment successful
- 400Invalid request
- 402Payment required or failed payment
- 409Duplicate transaction
- 500Payment gateway / server issue
Quiz
Test Your Status Code Knowledge
Five quick multiple-choice questions. Pick an answer and see instant feedback.
Which status code should be returned when a resource is successfully created?
Which status code means authentication is missing or invalid?
Which status code means the user is authenticated but not allowed?
Which status code is commonly used for rate limiting?
Which status code means the server is temporarily unavailable?
Answered 0 / 5
Interview Prep
HTTP Status Codes Interview Questions
Common interview questions on REST and HTTP — with crisp, interview-ready answers.
200 OK means the request succeeded. 201 Created means the request succeeded AND a new resource was created — typically returned from a POST that creates an entity, often with a Location header pointing to the new resource.
401 Unauthorized means the request lacks valid authentication. 403 Forbidden means the user is authenticated but does not have permission for that action.
When the request is malformed — invalid JSON, missing required fields, wrong types. For semantic validation issues (e.g. invalid email format), 422 Unprocessable Content is often a better choice.
An unhandled exception or unexpected condition on the server prevented the request from completing. It always indicates a server-side bug worth investigating.
200, 201, 204, 400, 401, 403, 404, 409, 422, 429, 500, and 503 cover the vast majority of REST API scenarios.
422 Unprocessable Content is preferred for semantic validation errors. 400 Bad Request is acceptable when the API treats validation generically.
502 Bad Gateway means the upstream returned an invalid response. 504 Gateway Timeout means the upstream did not respond in time.
FAQ
Frequently Asked Questions
Everything you need to know about HTTP status codes.
HTTP status codes are three-digit numbers servers return to indicate the result of an HTTP request — success, redirection, client error, or server error.
1xx Informational, 2xx Success, 3xx Redirection, 4xx Client Error, and 5xx Server Error.
200, 201, 204, 301, 302, 304, 400, 401, 403, 404, 409, 422, 429, 500, 502, 503, and 504.
200 OK with the resource representation in the response body.
201 Created when a new resource is created, or 200 OK when the action succeeded without creating a resource.
4xx codes indicate the client made an invalid request. 5xx codes indicate the server failed to fulfill an otherwise valid request.
Status codes are the first signal of whether an API behaves correctly. Tests assert on them to validate happy paths, error handling, authentication, and rate limiting.