How SSL Certificate Checker Works

This checker connects to the host you provide using TLS, reads the presented certificate (and optionally the full chain), and then parses the X.509 fields into a human-friendly report. It does not require access to your server; it only inspects what your public endpoint presents to clients.

Step-by-Step

• 1) Enter a domain: Provide the hostname you want to inspect (for example, example.com). You can also include a custom port if your TLS service is not on 443.
• 2) Start the check: The tool opens a secure connection and requests the peer certificate from the remote server.
• 3) Parse certificate fields: The certificate is decoded to extract issuer, subject, validity window, signature algorithm, public key details, and SAN entries.
• 4) Evaluate basics: The report highlights remaining validity days, whether the hostname matches the certificate, and the most common reasons for trust failures.
• 5) Review and export: Copy the formatted report or download it as a TXT file for documentation or support tickets.

Key Features

Fast certificate summary

Get a clear overview of the certificate subject, issuer, serial number, and validity dates in seconds. This is ideal when you need to confirm that a deployment actually went live and that the correct certificate is being served.

Expiration and renewal visibility

Renewal issues are one of the most common causes of outages. This tool highlights the Not Before and Not After timestamps and estimates how many days are left, helping you plan renewals before browsers begin showing warnings.

SAN and hostname matching insights

Modern certificates usually rely on Subject Alternative Names (SANs). The checker lists SAN entries so you can verify that all expected hostnames (like www, apex domains, or subdomains) are properly covered.

Optional chain visibility

Many TLS problems stem from incomplete chains or mis-ordered intermediates. When enabled, chain inspection helps you see which intermediate and root certificates are involved and whether the server is presenting them as expected.

Shareable report output

The output is formatted as plain text so you can paste it into incident reports, customer support messages, or internal documentation. Downloading the report keeps a snapshot of what was served at the time you checked.

Use Cases

• Post-renewal validation: Confirm that a newly issued certificate is live after renewal or automation (for example, after an ACME/Let’s Encrypt run).
• Debug browser warnings: Identify expired certificates, hostname mismatches, or missing intermediates that trigger “Your connection is not private”.
• Multi-domain coverage checks: Verify that one certificate properly covers several hostnames via SANs, including staging or regional subdomains.
• Load balancer and CDN audits: Ensure that your edge (CDN) and origin are serving the expected certificates, especially during migrations.
• Security reviews: Record issuer details, signature algorithms, and key sizes for compliance and periodic review.
• Vendor troubleshooting: Provide a readable certificate report when working with hosting providers or third-party platforms.

Whether you operate a single website or a complex multi-service stack, a quick certificate report can prevent outages and make TLS issues far easier to communicate and resolve.

Optimization Tips

Renew early and automate

Plan renewals well before expiration, and prefer automated renewals where possible. Even when automation is in place, perform periodic spot checks to ensure the active certificate matches your expectations and is deployed on every endpoint.

Cover all required hostnames

List the exact hostnames your users access and confirm they appear in SANs. Remember that a certificate for example.com typically does not cover www.example.com unless explicitly included.

Serve the full chain

Many clients rely on the server to provide intermediates. If you see trust failures on specific devices or networks, verify that your web server or load balancer is configured to present the complete certificate chain.

FAQ