SSL证书检查工具
检查任意域名的SSL/TLS证书：颁发机构、有效期以及距到期的天数。
如何使用本工具
- 1
Type a domain or URL into the input box, for example example.com or https://example.com.
- 2
Click Analyze to open a TLS connection to that host on port 443 and fetch its certificate.
- 3
Read the subject and issuer panels, then check the Valid from, Valid to, and Days remaining boxes.
- 4
Scan the SAN line to confirm the certificate actually covers the hostname you queried.
什么是SSL证书检查工具？
每个HTTPS网站都拥有一份证明服务器身份的SSL证书。证书会过期（Let's Encrypt：每90天；商业证书：通常每年）。当证书过期而未续期时，浏览器会显示令人警觉的安全警告。本工具会报告证书的颁发机构、有效期、剩余天数以及SAN（主题备用名称）。
常见使用场景
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.