1011xx InformationalInfo
HTTP 101 Switching Protocols
Defined in RFC 7231
What Does HTTP 101 Mean?
The server is switching protocols as requested by the client via the Upgrade header.
Common Causes
- 1WebSocket connection upgrade from HTTP
- 2Switching from HTTP/1.1 to HTTP/2
- 3Client requesting protocol change via Upgrade header
Impact
- ⚠No visible impact — connection is being upgraded transparently
- ⚠WebSocket connections begin after this response
Ad Space – header
Developer Fix
For web developers and application engineers
- 1Ensure WebSocket handshake logic is correct
- 2Handle protocol upgrade failures gracefully
- 3Verify Upgrade header values match server expectations
Server Admin Fix
For system administrators and DevOps engineers
- 1Ensure server supports the requested protocol upgrade
- 2Configure load balancers to allow WebSocket upgrades
- 3Check firewall rules for upgraded protocol traffic
Ad Space – after-fix
Frequently Asked Questions
When does 101 Switching Protocols occur?
Most commonly when establishing a WebSocket connection. The client sends an HTTP request with an Upgrade header, and the server responds with 101 to confirm the protocol switch.
Why is my WebSocket not getting a 101 response?
Check that your server supports WebSocket, the Upgrade and Connection headers are correct, and no proxy or load balancer is stripping the Upgrade header.
Related HTTP Status Codes
About the Author
Web Infrastructure Team
Verified against official RFC specifications and real-world server configurations. HTTP status code behavior confirmed across Apache, Nginx, and Cloudflare.