Free SSL Certificate Checker — Verify HTTPS Security Instantly
Check any domain's SSL certificate status, expiry date, issuer, and hostname validity in one click. No installation required.
Why SSL Certificate Health Matters
What This SSL Checker Verifies
We perform a live TLS handshake against your domain and return detailed certificate data.
Understanding SSL Status Results
Each status means something different — here is what to do with each one.
| Status | Meaning |
|---|---|
| valid | Trusted CA, hostname matches, not expired, chain verified |
| expired | Certificate passed its valid-to date |
| not_yet_valid | Certificate issued but start date is in the future |
| self_signed | Not signed by a trusted Certificate Authority |
| hostname_mismatch | Domain queried is not listed in CN or SANs |
| invalid | Certificate chain verification failed |
| unreachable | Domain did not respond on port 443 |
Who This Tool Is For
SSL monitoring is relevant to anyone who runs a website, API, or email infrastructure.
Web developers checking newly deployed domains
DevOps and sysadmins monitoring certificate renewal
Security teams auditing SSL posture across multiple domains
Marketing teams verifying landing page HTTPS before ad campaigns
Domain owners checking expiry dates before renewal deadlines
What to Do After Checking
Different results require different remediation steps.
Expired
Renew immediately. Run certbot renew or reissue via your hosting provider's dashboard. Ensure auto-renewal is active to prevent recurrence.
Self-Signed
Replace with a certificate from a trusted CA. Let's Encrypt provides free, auto-renewing certificates for any domain.
Hostname Mismatch
Reissue the certificate and include the mismatched domain in the Subject Alternative Names. Wildcard certs (*.example.com) cover all direct subdomains.
Invalid Chain
Download and install the missing intermediate certificate bundle from your CA's documentation. Most chain issues are caused by missing intermediates, not the leaf cert.
Expiring Within 30 Days
Enable auto-renewal via ACME/Certbot or set a calendar reminder. Proactive renewal prevents the expired status shown here from ever reaching production.
Frequently Asked Questions
What does this SSL checker tool do?
It performs a live TLS handshake against your domain on port 443 and returns the certificate's status, issuer, valid-from and valid-to dates, days remaining, Subject Alternative Names (SANs), and whether the certificate is self-signed or has a hostname mismatch.
What does a 'Valid' SSL status mean?
Valid means the certificate is issued by a trusted Certificate Authority (CA), the hostname on the certificate matches the domain queried, the certificate has not expired, the start date has passed, and the certificate chain can be verified against public CA roots.
What should I do if my SSL certificate is expired?
certbot renew or check your auto-renewal cron. For paid certificates, log in to your CA dashboard and reissue.
What is a self-signed certificate and why is it a problem?
A self-signed certificate is signed by its own private key rather than by a trusted CA. Browsers do not trust them by default and show 'Your connection is not private' warnings. Self-signed certs are fine for internal development environments but must never be used on public-facing domains.
What causes an SSL hostname mismatch?
A hostname mismatch occurs when the domain you queried (e.g., www.example.com) is not listed in the certificate's Common Name (CN) or Subject Alternative Names (SANs). This happens when certificates are issued for the root domain but not the www subdomain (or vice versa), or when using a wildcard cert that does not cover the specific subdomain queried.
How far in advance should I renew my SSL certificate?
Renew at least 30 days before expiry. Most automated systems (Let's Encrypt via Certbot, AWS ACM auto-renewal) handle this automatically. For manually managed certificates, set a calendar reminder at 60 days and 30 days before the expiry date shown in this tool.
Does SSL status affect email deliverability?
Indirectly yes. Many email authentication flows (MTA-STS, DANE, HTTPS-based DMARC reporting endpoints) require valid TLS certificates. Additionally, if your email signup or landing page has a broken SSL cert, users may abandon the form, reducing list growth and engagement rates.
What is the difference between SSL and TLS?
SSL (Secure Sockets Layer) is the deprecated predecessor to TLS (Transport Layer Security). All modern 'SSL certificates' actually use TLS 1.2 or TLS 1.3. The term 'SSL certificate' persists in common usage even though the underlying protocol is TLS. This tool tests TLS connectivity, which is what all current browsers and email clients use.
Can I check SSL for subdomains?
Yes. Enter the full subdomain — for example, mail.example.com or app.example.com. The tool connects to port 443 of that hostname specifically. A wildcard cert (*.example.com) will show as valid for any direct subdomain but not for sub-subdomains.
Does this tool store my domain data?
No. All lookups are performed in real time and no domain data is stored or used for profiling. Each query is stateless.