The Error “525” is a unique error code designed to inform the website owner and visitors that the website was unable to successfully establish a connection from the visitor, through the Cloudflare system, to the hosting server.
This error can only occur when a Cloudflare service customer is using the Full SSL or Full SSL (Strict) SSL options.
Note: For more information regarding the Cloudflare SSL options please see the following link:
Cloudflare SSL Options
If you do receive a report from a site visitor that the Error code 525 is displaying, please review the following most common causes:
The hosting server either doesn’t have an SSL installed, or it is installed improperly
The hosting server either doesn’t support or is improperly configured to handle SNI (Server Name Indication)
The hosting server is not supporting acceptable cipher suites that are required by Cloudflare.
There can be other reasons why the 525 error code is being presented. In short, when attempting to troubleshoot this error keep in mind that this error is occurring because the Cloudflare service is expecting a secure connection based on a recognizable cipher/hash. If for whatever reason, the Cloudflare system is unable to establish this secure connection but is receive data from the server, it will present the 525 error.