406
SIP
406 Not Acceptable
The resource identified by the request is only capable of generating responses with content characteristics not acceptable according to the Accept header.
On this page
When You See This Code
When content negotiation fails — the server cannot produce a response matching the Accept header fields in the request.
How to Fix
Review the Accept headers in your request and broaden the acceptable content types.
Specification
Compare With
Guides
401 Unauthorized vs 403 Forbidden: When to Use Each
Security & Authentication
SIP Response Codes: Understanding VoIP Call Flow
Real-Time Protocols
SIP Call Flow: Understanding Session Setup
Real-Time Protocols
WebRTC Signaling with SIP and WebSocket
Real-Time Protocols
RFC 3261: SIP Protocol Deep Dive
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TLS 1.3: Faster, Simpler, More Secure
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Frequently Asked Questions
What is SIP 406 Not Acceptable?
The resource identified by the request is only capable of generating responses with content characteristics not acceptable according to the Accept header.
When do you see SIP 406 Not Acceptable?
When content negotiation fails — the server cannot produce a response matching the Accept header fields in the request.
How to fix SIP 406 Not Acceptable?
Review the Accept headers in your request and broaden the acceptable content types.