Network Tools

SSL Certificate Checker

Check SSL/TLS certificate validity and expiry for any website. Shows issuer, Subject Alternative Names (SANs), and TLS protocol version — instant lookup.

Expiry Date
Issuer
SANs
TLS Protocol
Instant Lookup

Domain

Domain only, without https://

Enter a domain name to check its SSL certificate

SSL certificate checker

Inspect the certificate presented by a domain on port 443. Results include validity dates, days remaining, issuer and subject fields, subject alternative names, serial number, fingerprint, and negotiated protocol when available.

Why expiration matters

Expired certificates cause browser warnings and can break API clients, webhooks, and automated jobs. Check production domains before renewal windows and verify SAN coverage after certificate changes.

The request is made through the site's SSL checker endpoint; certificate details are displayed without uploading files.

Frequently Asked Questions

What does this tool check?: It checks the SSL/TLS certificate for a domain — including the issuer, validity period, subject, SANs (Subject Alternative Names), and whether the certificate is currently valid.
What is an SSL certificate?: An SSL/TLS certificate is a digital certificate that authenticates a website's identity and enables encrypted (HTTPS) connections between client and server.
What does 'certificate chain' mean?: A certificate chain connects your domain certificate to a trusted root CA (Certificate Authority) via intermediate certificates. All links must be valid for browsers to trust the certificate.
How far in advance should I renew?: Renew at least 30 days before expiry. Most certificates are valid for 90 days (Let's Encrypt) or 1–2 years (paid CAs).

Disclaimer

This tool is provided for general informational and utility purposes only. Results may be inaccurate, incomplete, outdated, or contain errors. Always verify results before relying on or using them.

Some tools may use AI, automated processing, third-party services, or server-side processing. Do not rely on these tools as a substitute for professional advice.

Use at your own risk. BestToolOnline makes no guarantees regarding the accuracy, reliability, completeness, availability, or suitability of results, to the maximum extent permitted by applicable law.

See our Terms of Service and Privacy Policy for complete details.

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SSL certificate checker

Why expiration matters

Expired certificates cause browser warnings and can break API clients, webhooks, and automated jobs. Check production domains before renewal windows and verify SAN coverage after certificate changes.

The request is made through the site's SSL checker endpoint; certificate details are displayed without uploading files.

Frequently Asked Questions

What does this tool check?

It checks the SSL/TLS certificate for a domain — including the issuer, validity period, subject, SANs (Subject Alternative Names), and whether the certificate is currently valid.

What is an SSL certificate?

An SSL/TLS certificate is a digital certificate that authenticates a website's identity and enables encrypted (HTTPS) connections between client and server.

What does 'certificate chain' mean?

A certificate chain connects your domain certificate to a trusted root CA (Certificate Authority) via intermediate certificates. All links must be valid for browsers to trust the certificate.

How far in advance should I renew?

Renew at least 30 days before expiry. Most certificates are valid for 90 days (Let's Encrypt) or 1–2 years (paid CAs).

Disclaimer

Some tools may use AI, automated processing, third-party services, or server-side processing. Do not rely on these tools as a substitute for professional advice.