List of SIP response codes


The Session Initiation Protocol is a signalling protocol used for controlling communication sessions such as Voice over IP telephone calls. SIP is based on request/response transactions, in a similar manner to the Hypertext Transfer Protocol. Each transaction consists of a SIP request, and at least one response.
SIP requests and responses may be generated by any SIP user agent; user agents are divided into clients, which initiate requests, and servers, which respond to them. A single user agent may act as both UAC and UAS for different transactions: for example, a SIP phone is a user agent that will be a UAC when making a call, and a UAS when receiving one. Additionally, some devices will act as both UAC and UAS for a single transaction; these are called Back-to-Back User Agents.
SIP responses specify a three-digit integer response code, which is one of a number of defined codes that detail the status of the request. These codes are grouped according to their first digit as "provisional", "success", "redirection", "client error", "server error" or "global failure" codes, corresponding to a first digit of 1–6; these are expressed as, for example, "1xx" for provisional responses with a code of 100–199. The SIP response codes are consistent with the HTTP response codes, although not all HTTP response codes are valid in SIP.
SIP responses also specify a "reason phrase", and a default reason phrase is defined with each response code. These reason phrases can be varied, however, such as to provide additional information or to provide the text in a different language.
The SIP response codes and corresponding reason phrases were initially defined in RFC 3261. That RFC also defines a SIP Parameters Internet Assigned Numbers Authority registry to allow other RFC to provide more response codes.
This list includes all the SIP response codes defined in IETF RFCs and registered in the SIP Parameters IANA registry as of 2017. This list also includes SIP response codes defined in obsolete SIP RFCs, which are therefore not registered with the IANA; these are explicitly noted as such.

1xx—Provisional Responses

; 100 Trying
; 180 Ringing
; 181 Call is Being Forwarded
; 182 Queued
; 183 Session Progress
; 199 Early Dialog Terminated

2xx—Successful Responses

; 200 OK
; 202 Accepted
; 204 No Notification

3xx—Redirection Responses

; 300 Multiple Choices
; 301 Moved Permanently
; 302 Moved Temporarily
; 305 Use Proxy
; 380 Alternative Service

4xx—Client Failure Responses

; 400 Bad Request
; 401 Unauthorized
; 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 Conditional Request Failed
; 413 Request Entity Too Large
; 414 Request-URI Too Long
; 415 Unsupported Media Type
; 416 Unsupported URI Scheme
; 417 Unknown Resource-Priority
; 420 Bad Extension
; 421 Extension Required
; 422 Session Interval Too Small
; 423 Interval Too Brief
; 424 Bad Location Information
; 428 Use Identity Header
; 429 Provide Referrer Identity
; 430 Flow Failed
; 433 Anonymity Disallowed
; 436 Bad Identity-Info
; 437 Unsupported Certificate
; 438 Invalid Identity Header
; 439 First Hop Lacks Outbound Support
; 440 Max-Breadth Exceeded
; 469 Bad Info Package
; 470 Consent Needed
; 480 Temporarily Unavailable
; 481 Call/Transaction Does Not Exist
; 482 Loop Detected
; 483 Too Many Hops
; 484 Address Incomplete
; 485 Ambiguous
; 486 Busy Here
; 487 Request Terminated
; 488 Not Acceptable Here
; 489 Bad Event
; 491 Request Pending
; 493 Undecipherable
; 494 Security Agreement Required

5xx—Server Failure Responses

; 500 Internal Server Error
; 501 Not Implemented
; 502 Bad Gateway
; 503 Service Unavailable
; 504 Server Time-out
; 505 Version Not Supported
; 513 Message Too Large
; 555 Push Notification Service Not Supported
; 580 Precondition Failure

6xx—Global Failure Responses

; 600 Busy Everywhere
; 603 Decline
; 604 Does Not Exist Anywhere
; 606 Not Acceptable
; 607 Unwanted
; 608 Rejected