HTTP 505 HTTP Version Not Supported vs 526 Invalid SSL Certificate
Both HTTP 505 (HTTP Version Not Supported) and 526 (Invalid SSL Certificate) belong to the 5xx Server Error category. 505 indicates that the server does not support the HTTP version used in the request. Meanwhile, 526 means that cloudflare-specific. The origin's SSL certificate could not be validated.
Description
The server does not support the HTTP version used in the request.
When You See It
When a client uses an HTTP version the server doesn't support.
How to Fix
Use a supported HTTP version (typically HTTP/1.1 or HTTP/2).
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
HTTP 505: The server does not support the HTTP version used in the request.
HTTP 526: Cloudflare-specific. The origin's SSL certificate could not be validated.
You encounter 505 when when a client uses an HTTP version the server doesn't support.
You encounter 526 when when using Cloudflare Full (Strict) mode with an invalid origin certificate.
When to Use Which
For 505 (HTTP Version Not Supported): Use a supported HTTP version (typically HTTP/1.1 or HTTP/2). For 526 (Invalid SSL Certificate): Install a valid SSL certificate on the origin, or use Cloudflare Origin CA certificate.