What are the Status code for API testing?

Status codes are issued by a server in response to a client's request made to the server. ... All HTTP response status codes are separated into five classes or categories. The first digit of the status code defines the class of response, while the last two digits do not have any classifying or categorization role.

The status codes are divided into the five categories.

• 1xx: Informational – Communicates transfer protocol-level information.
• 2xx: Success – Indicates that the client’s request was accepted successfully.
• 3xx: Redirection – Indicates that the client must take some additional action in order to complete their request.
• 4xx: Client Error – This category of error status codes points the finger at clients.
• 5xx: Server Error – The server takes responsibility for these error status codes.

#1) 100 Series

These are temporary Responses

• 100 Continue
• 101 Switching Protocols
• 102 Processing

#2) 200 Series

The client accepts the Request, being processed successfully at the server.

• 200 – OK
• 201 – Created
• 202 – Accepted
• 203 – Non-Authoritative Information
• 204 – No Content
• 205 – Reset Content
• 206 – Partial Content
• 207 – Multi-Status
• 208 – Already Reported
• 226 – IM Used

#3) 300 Series

Most of the codes related to this series are for URL Redirection.

• 300 – Multiple Choices
• 301 – Moved Permanently
• 302 – Found
• 303 – Check Other
• 304 – Not Modified
• 305 – Use Proxy
• 306 – Switch Proxy
• 307 – Temporary Redirect
• 308 – Permanent Redirect

#4) 400 Series

These are specific to client-side error.

• 400 – Bad Request
• 401 – Unauthorised
• 402 – Payment Required
• 403 – Forbidden
• 404 – Not Found
• 405 – Method Not Allowed
• 406 – Not Acceptable
• 407 – Proxy Authentication Required
• 408 – Request Timeout
• 409 – Conflict
• 410 – Gone
• 411 – Length Required
• 412 – Precondition Failed
• 413 – Payload Too Large
• 414 – URI Too Long
• 415 – Unsupported Media Type
• 416 – Range Not Satisfiable
• 417 – Expectation Failed
• 418 – I’m a teapot
• 421 – Misdirected Request
• 422 – Unprocessable Entity
• 423 – Locked
• 424 – Failed Dependency
• 426 – Upgrade Required
• 428 – Precondition Required
• 429 – Too Many Requests
• 431 – Request Header Fields Too Large
• 451 – Unavailable For Legal Reasons
  
  

#5) 500 Series

These are specific to the server-side error.

• 500 – Internal Server Error
• 501 – Not Implemented
• 502 – Bad Gateway
• 503 – Service Unavailable
• 504 – Gateway Timeout
• 505 – HTTP Version Not Supported
• 506 – Variant Also Negotiates
• 507 – Insufficient Storage
• 508 – Loop Detected
• 510 – Not Extended
• 511 –  Network Authentication Required

Apart from this, there are several different codes that exist but those will deviate us from our current discussion.