Free SSL Certificate Checker — Check Expiry, Issuer & SANs Online
Last Updated: May 2026 · 5 min read
An expired SSL certificate causes browsers to show terrifying red warning pages, tanks your SEO rankings, and breaks API integrations instantly. Our free SSL certificate checker lets you inspect any domain's certificate — expiry date, issuer, Subject Alternative Names, and validity status — in seconds. No signup required.
What Is an SSL Certificate?
An SSL/TLS certificate is a digital credential that: 1. Encrypts all data transmitted between a browser and your server (HTTPS) 2. Authenticates your server's identity — proving you are who you claim to be 3. Triggers the padlock icon in browser address bars
Without a valid SSL certificate, modern browsers (Chrome, Firefox, Safari) show a "Your connection is not private" warning that drives away virtually all visitors.
What Our Free SSL Checker Shows
When you check a domain, you get:
| Field | What It Means |
|---|---|
| Expiry Date | When the certificate becomes invalid |
| Days Remaining | Color-coded: green (>30 days), orange (7–30 days), red (<7 days) |
| Issued Date | When the certificate was issued |
| Subject CN | The primary domain the certificate covers |
| Issuer | The Certificate Authority (CA) that issued it |
| SANs | All domains and subdomains covered (Subject Alternative Names) |
| Serial Number | Unique identifier for the certificate |
Why SSL Certificates Expire
SSL certificates have a validity period set by the CA/Browser Forum. As of 2020, the maximum validity is 398 days (approximately 13 months). Before 2020, certificates could be valid for up to 3 years.
Why are they time-limited? If a private key is compromised, shorter validity periods limit how long an attacker can use a fraudulent certificate. There's ongoing discussion about reducing validity to 90 or even 45 days.
Common SSL Certificate Problems
1. Certificate Expired
The most common issue. After expiry, browsers reject the site completely. All HTTPS traffic fails.
Fix: Renew immediately. If using Let's Encrypt, automate with certbot renew on a cron job.
2. Certificate Domain Mismatch
The certificate was issued for example.com but you're accessing www.example.com or api.example.com.
Fix: Use a wildcard certificate (*.example.com) or a multi-domain SAN certificate.
3. Incomplete Certificate Chain
The server isn't sending intermediate certificates, causing validation failures in some clients.
Fix: Configure your web server to include the full chain file, not just the end-entity certificate.
4. Self-Signed Certificate
Browsers don't trust self-signed certificates. Fine for development, not for production.
Fix: Use a trusted CA — Let's Encrypt is free and trusted everywhere.
5. Weak Cipher Suite
Older certificates using SHA-1 or certificates with key lengths under 2048 bits may be rejected.
Fix: Reissue with SHA-256 and RSA 2048-bit (or ECDSA P-256) key.
Free SSL Certificate Authorities
You don't need to pay for SSL. These free CAs are trusted by all major browsers:
| Authority | Notes |
|---|---|
| Let's Encrypt | Most popular. 90-day validity. Auto-renewal via certbot. |
| ZeroSSL | Free 90-day certs. Dashboard available. |
| Google Trust Services | Available for Google Cloud users. |
| Buypass Go SSL | 180-day certificates, EU-based. |
How to Check SSL Certificate Expiry Free
- Go to SolutionGigs Free SSL Checker
- Enter any domain (e.g.,
example.com— nohttps://needed) - Click Check SSL
- See expiry, issuer, SANs, and validity status instantly
- No login, no limits, 100% free
You can also check SSL from the command line:
echo | openssl s_client -connect example.com:443 -servername example.com 2>/dev/null | openssl x509 -noout -dates
Monitoring SSL Certificate Expiry
A single manual check isn't enough — you need ongoing monitoring to prevent surprise expirations. Best practices:
- Set calendar reminders at 60 and 30 days before expiry
- Enable auto-renewal for Let's Encrypt with
certbot renewin a daily/weekly cron job - Use monitoring services — UptimeRobot, StatusCake, and Better Uptime all offer free SSL expiry alerts
- Check all your domains — don't forget staging, API subdomains, and CDN origins
What Are Subject Alternative Names (SANs)?
SANs are additional domains and subdomains covered by a single certificate. Modern certificates must use SANs (the CN field alone is no longer sufficient per RFC 2818).
Example: A wildcard cert for *.example.com with SANs might cover:
- www.example.com
- api.example.com
- blog.example.com
- example.com (the root domain, listed explicitly)
Our free SSL checker shows all SANs so you can verify which domains are covered.
Try the Free SSL Certificate Checker
SolutionGigs Free SSL Checker — check any domain's SSL certificate expiry and details in seconds. No signup, 100% free.
Frequently Asked Questions
What is an SSL certificate? An SSL/TLS certificate is a digital certificate that authenticates a website's identity and enables HTTPS — encrypting all data between the visitor's browser and the server. Websites without it show 'Not Secure' in Chrome and are penalized by Google.
What happens when an SSL certificate expires? Browsers immediately show a 'Your connection is not private' error, blocking all visitors. Search engines may demote or deindex the site. Email delivery from the domain can also fail. Always renew at least 30 days before expiry.
What are Subject Alternative Names (SANs)? SANs allow a single SSL certificate to cover multiple domain names and subdomains. For example, one certificate can secure example.com, www.example.com, shop.example.com, and blog.example.com simultaneously.
How do I check if my SSL certificate is about to expire? Enter your domain name in our free SSL Certificate Checker — it instantly shows the exact expiry date, days remaining, issuer authority, certificate grade, and all SANs. No login needed.
What is the difference between DV, OV, and EV SSL certificates? DV (Domain Validation) verifies domain ownership only — issued in minutes, cheapest. OV (Organization Validation) verifies the business identity — issued in 1–3 days. EV (Extended Validation) requires full legal verification — shows a green padlock with the company name in older browsers.
Mohammed Yaseen
Founder, SolutionGigs
Mohammed has been building developer tools since 2018 and writes about JSON, JWT, regex, SQL, APIs, and web development utilities. LinkedIn →