Security Tools

SSL Certificate Checker

Inspect a website's SSL certificate and check its expiry.

Free to use
No sign-up

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About this tool

Enter a website address to see the security details its server presents when a browser connects over HTTPS: who issued them, which names they cover, when they started and how many days remain before they expire.

How to use it

Type a domain such as example.com.
Run the check.
Review the issuer, covered names and validity dates.

What the report shows

Common name – the main hostname the server identifies as.
Issuer – the authority that signed it, for example Let's Encrypt or DigiCert.
Valid from / valid until – the start and end dates.
Days remaining – a quick countdown so renewals are never missed.
Alternative names – every extra hostname covered, such as the www version or subdomains.

Why check it?

When HTTPS credentials expire or do not cover the hostname a visitor types, browsers show a full-page warning and many people leave immediately. Checking ahead of time lets you renew early, confirm that automatic renewal is working, and make sure the www and non-www versions are both covered.

SSL and TLS

People still say "SSL", but modern sites use its successor, TLS. The checker works with both and reports what the server actually sends.

Limitations

The tool connects on port 443 and reads what the server presents at that moment. Some hosts serve different credentials per subdomain or per region. A valid result confirms that the connection is encrypted; it does not mean the site is free from malware or other security problems.

A worked example

An online shop runs the check a week before a big sale and sees only nine days remaining. Automatic renewal had silently failed after a server move. Renewing in time avoided a browser warning on the busiest weekend of the year.

Reading the dates

Free authorities such as Let's Encrypt issue credentials valid for 90 days and renew them automatically around day 60. Paid ones usually last up to a year. If the remaining time drops below about two weeks and nothing has changed, investigate the renewal process.

Fixing common issues

Name mismatch – make sure both example.com and www.example.com are listed as alternative names.
Expired – renew, then restart or reload the web server so it loads the new files.
Old copy still served – clear the cache or update the setting at your CDN or proxy.
Chain errors – install the intermediate files supplied by your authority.

Good habits

Check after every server, host or CDN change.
Set a calendar reminder a month before paid credentials expire.
Monitor every subdomain you use, not just the main site.

Related tools

SSL Checker – a quick second opinion
WWW Redirect Checker – confirm one consistent address
HTTP Headers Checker – review security headers

Glossary

CA – certificate authority, the organisation that signs credentials.
SAN – subject alternative names, the list of hostnames covered.
Intermediate – a link in the trust chain between your server and the CA.

Frequently asked questions

The common name, issuer, start and end dates, days remaining and every alternative hostname covered.

Enter the domain and read the 'valid until' date and the days-remaining countdown in the results.

No. It confirms the connection is encrypted, but it does not scan for malware, vulnerabilities or phishing.

Free ones usually last 90 days and renew automatically; paid ones typically last up to a year.

The server or CDN may still be serving the old copy; reload the server or clear the CDN cache.

Subject alternative names: the list of hostnames the credentials cover.