Practical guidance
Check the exact hostname and port, including certificate alternative names. A certificate for one subdomain may not cover another. Cached intermediates can conceal an incomplete trust chain on some clients.
Before using this tool
Define what you need from SSL certificate checker and prepare the relevant input. When diagnosing a live service, record the test time and connection conditions so you can compare results after configuration changes. Check findings against the documentation for your software.
Tool availability
This is currently an information page. No working form, calculations or submission to diagnostic services is available yet. The interface and supported input formats will be documented when functionality is released.