HTTP 101 Switching Protocols vs 526 Invalid SSL Certificate
HTTP 101 (Switching Protocols) is a 1xx Informational response, while 526 (Invalid SSL Certificate) 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, 526 means that cloudflare-specific. The origin's SSL certificate could not be validated.
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
Cloudflare-specific. The origin's SSL certificate could not be validated.
When You See It
When using Cloudflare Full (Strict) mode with an invalid origin certificate.
How to Fix
Install a valid SSL certificate on the origin, or use Cloudflare Origin CA certificate.
Key Differences
101 is a 1xx Informational response, while 526 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 526: Cloudflare-specific. The origin's SSL certificate could not be validated.
You encounter 101 when when upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
You encounter 526 when when using Cloudflare Full (Strict) mode with an invalid origin certificate.
When to Use Which
For 101 (Switching Protocols): This is normal behavior during protocol upgrades. Ensure your client supports the target protocol. For 526 (Invalid SSL Certificate): Install a valid SSL certificate on the origin, or use Cloudflare Origin CA certificate.