HTTP 101 Switching Protocols vs 511 Network Authentication Required
HTTP 101 (Switching Protocols) is a 1xx Informational response, while 511 (Network Authentication Required) is a 5xx Server Error response. 101 indicates that the server understands the Upgrade header field request and indicates which protocol it is switching to. In contrast, 511 means that the client needs to authenticate to gain network access. Used by captive portals (hotel/airport WiFi).
Description
The server understands the Upgrade header field request and indicates which protocol it is switching to.
When You See It
When upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
How to Fix
This is normal behavior during protocol upgrades. Ensure your client supports the target protocol.
Description
The client needs to authenticate to gain network access. Used by captive portals (hotel/airport WiFi).
When You See It
When connecting to WiFi that requires login (airport, hotel, coffee shop).
How to Fix
Open a browser and complete the captive portal login process.
Key Differences
101 is a 1xx Informational response, while 511 is a 5xx Server Error response.
HTTP 101: The server understands the Upgrade header field request and indicates which protocol it is switching to.
HTTP 511: The client needs to authenticate to gain network access. Used by captive portals (hotel/airport WiFi).
You encounter 101 when when upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
You encounter 511 when when connecting to WiFi that requires login (airport, hotel, coffee shop).
When to Use Which
For 101 (Switching Protocols): This is normal behavior during protocol upgrades. Ensure your client supports the target protocol. For 511 (Network Authentication Required): Open a browser and complete the captive portal login process.