HTTP 304 Not Modified vs 526 Invalid SSL Certificate
HTTP 304 (Not Modified) is a 3xx Redirection response, while 526 (Invalid SSL Certificate) is a 5xx Server Error response. 304 indicates that the resource has not been modified since the last request. The client can use its cached copy. In contrast, 526 means that cloudflare-specific. The origin's SSL certificate could not be validated.
Description
The resource has not been modified since the last request. The client can use its cached copy.
When You See It
When the browser cache is still valid (If-None-Match / If-Modified-Since headers match).
How to Fix
No fix needed. This saves bandwidth by confirming the cached version is still current.
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
304 is a 3xx Redirection response, while 526 is a 5xx Server Error response.
HTTP 304: The resource has not been modified since the last request. The client can use its cached copy.
HTTP 526: Cloudflare-specific. The origin's SSL certificate could not be validated.
You encounter 304 when when the browser cache is still valid (If-None-Match / If-Modified-Since headers match).
You encounter 526 when when using Cloudflare Full (Strict) mode with an invalid origin certificate.
When to Use Which
For 304 (Not Modified): No fix needed. This saves bandwidth by confirming the cached version is still current. For 526 (Invalid SSL Certificate): Install a valid SSL certificate on the origin, or use Cloudflare Origin CA certificate.