| Code | RFC 3261: SIP | RFC2616: HTTP 1.1 |
| 1xx | Provisional |
| 100 | Trying | Continue |
| 101 | - | Switching Protocols |
| 180 | Ringing | - |
| 181 | Call Is Being Forwarded | - |
| 182 | Queued | - |
| 183 | Session Progress | - |
| 2xx | Successful 2xx |
| 200 | OK | OK |
| 201 | - | Created |
| 3xx | Redirection |
| 300 | Multiple Choices | Multiple Choices |
| 301 | Moved Permanently | Moved Permanently |
| 302 | Moved Temporarily | Found |
| 305 | Use Proxy | Use Proxy |
| 380 | Alternative Service | |
| 4xx | Request Failure |
| 400 | Bad Request | Bad Request |
| 401 | Unauthorized | Unauthorized |
| 402 | Payment Required | Payment Required |
| 403 | Forbidden | Forbidden |
| 404 | Not Found | Not Found |
| 405 | Method Not Allowed | Method Not Allowed |
| 406 | Not Acceptable | Not Acceptable |
| 407 | Proxy Authentication Required | Proxy Authentication Required |
| 408 | Request Timeout | Request Timeout |
| 410 | Gone | Gone |
| 413 | Request Entity Too Large | Request Entity Too Large |
| 414 | Request-URI Too Long | Request-URI Too Long |
| 415 | Unsupported Media Type | Unsupported Media Type |
| 416 | Unsupported URI Scheme | Requested Range Not Satisfiable |
| 420 | Bad Extension | |
| 421 | Extension Required | There are too many connections from your internet address |
| 423 | Interval Too Brief | Locked |
| 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 | |
| 491 | Request Pending | |
| 493 | Undecipherable | |
| 5xx | Server Failure |
| 500 | Server Internal Error | Internal Server Error |
| 501 | Not Implemented | Not Implemented |
| 502 | Bad Gateway | Bad Gateway |
| 503 | Service Unavailable | Service Unavailable |
| 504 | Server Time-out | Gateway Timeout |
| 505 | Version Not Supported | HTTP Version Not Supported |
| 513 | Message Too Large | - |
| 6xx | Global Failures |
| 600 | Busy Everywhere | - |
| 603 | Decline | - |
| 604 | Does Not Exist Anywhere | - |
| 606 | Not Acceptable | - |