SSL証明書チェッカー

このツールの使い方

1. 1

   Type a domain or URL into the input box, for example example.com or https://example.com.

2. 2

   Click Analyze to open a TLS connection to that host on port 443 and fetch its certificate.

3. 3

   Read the subject and issuer panels, then check the Valid from, Valid to, and Days remaining boxes.

4. 4

   Scan the SAN line to confirm the certificate actually covers the hostname you queried.

SSL証明書チェッカーとは何ですか？

よくある活用例

• Confirm a newly issued or renewed certificate is actually live on the server before announcing a launch.

• Catch a certificate that is within 30 days of expiry (the tool flags it in red) so you can renew before users hit warnings.

• Verify the SAN list includes every subdomain you serve, such as www and api, after editing a multi-domain cert.

• Check which Certificate Authority signed a third-party or vendor endpoint you depend on.

• Spot-check that an automated renewal job (for example Let's Encrypt via certbot) actually swapped in the new certificate.

• Read the exact valid-from and valid-to timestamps when debugging a clock-skew or not-yet-valid certificate error.

よくある質問