Technical Tip: How to validate the certificate date between FortiGate SSL Inspection and Client Browser

[kmohan]

Description	This article explains how to validate the expiration date of SSL-inspection certificates on FortiGate, with instructions for confirming the certificate status from the client’s browser.
Scope	FortiGate.
Solution	Download and install the FortiGate CA Certificate on the client pc. Certification shows the Validation date as below: Valid from 14-11-2025 to 15-11-2035. The valid date issued by CA shows 10 years. After installation on the client Pc under Trusted Root Certificate. Try to access any URL, like public websites. It will show a validity from 9/05/2025 to 12/05/2025. The CA issues the duration for the current websites; it will keep changing every time, but the same valid date will be visible on the browser:  Select Certification valid -> Certification Path.  Under the FortiGate Serial number, the Website SNI will be visible. Select the GortiGate Serial Number, CA Certificate validation shows the same as the Deep_Inspection Certificate. To verify the original Certificate Validation for the website, it can be verified from a third-party website.