HTTP 226 IM Used vs 511 Network Authentication Required
HTTP 226 (IM Used) is a 2xx Success response, while 511 (Network Authentication Required) is a 5xx Server Error response. 226 indicates that the server has fulfilled a GET request for the resource, and the response is a representation of the result of one or more instance-manipulations. In contrast, 511 means that the client needs to authenticate to gain network access. Used by captive portals (hotel/airport WiFi).
Description
The server has fulfilled a GET request for the resource, and the response is a representation of the result of one or more instance-manipulations.
When You See It
When using delta encoding to reduce bandwidth.
How to Fix
Rarely encountered. The response uses Instance Manipulations (IM) as specified.
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
226 is a 2xx Success response, while 511 is a 5xx Server Error response.
HTTP 226: The server has fulfilled a GET request for the resource, and the response is a representation of the result of one or more instance-manipulations.
HTTP 511: The client needs to authenticate to gain network access. Used by captive portals (hotel/airport WiFi).
You encounter 226 when when using delta encoding to reduce bandwidth.
You encounter 511 when when connecting to WiFi that requires login (airport, hotel, coffee shop).
When to Use Which
For 226 (IM Used): Rarely encountered. The response uses Instance Manipulations (IM) as specified. For 511 (Network Authentication Required): Open a browser and complete the captive portal login process.