HTTP 101 Switching Protocols vs 203 Non-Authoritative Information
HTTP 101 (Switching Protocols) is a 1xx Informational response, while 203 (Non-Authoritative Information) is a 2xx Success response. 101 indicates that the server understands the Upgrade header field request and indicates which protocol it is switching to. In contrast, 203 means that the response payload has been modified by a transforming proxy from the origin server's 200 response.
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 response payload has been modified by a transforming proxy from the origin server's 200 response.
When You See It
When a proxy or CDN modifies the response body (e.g., adds headers, transforms content).
How to Fix
Check if a proxy is modifying the response. Access the origin directly if you need the original content.
Key Differences
101 is a 1xx Informational response, while 203 is a 2xx Success response.
HTTP 101: The server understands the Upgrade header field request and indicates which protocol it is switching to.
HTTP 203: The response payload has been modified by a transforming proxy from the origin server's 200 response.
You encounter 101 when when upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
You encounter 203 when when a proxy or CDN modifies the response body (e.g., adds headers, transforms content).
When to Use Which
For 101 (Switching Protocols): This is normal behavior during protocol upgrades. Ensure your client supports the target protocol. For 203 (Non-Authoritative Information): Check if a proxy is modifying the response. Access the origin directly if you need the original content.