SIP Response-Code Lookup

How this SIP response code lookup helps

SIP response codes describe how a server, proxy, registrar or endpoint handled a request. Use this tool when reading PBX logs, provider traces or packet captures. It provides a plain language starting point, not a definitive diagnosis.

Recommended workflow

1. Record the exact time and direction of the call.
2. Identify which system generated the response.
3. Check authentication, DNS, routing, codec negotiation and NAT.
4. Compare the failing message with a successful call and review provider call records.

Frequently asked questions

Does 403 always mean incorrect credentials?

No. It can indicate a policy restriction, blocked source address, disallowed destination, account permission or fraud control.

What does 488 usually indicate?

It commonly means that the destination could not accept the offered media because of codec, media format or SDP incompatibility.

For related checks, see the VoIP troubleshooting guide and VoIP fundamentals guide.