SSL Certificate Checker
Inspect the SSL certificate for any domain - expiry, issuer, subject alternative names and more.
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About the SSL Certificate Checker
An SSL certificate is what allows a website to use HTTPS, encrypting traffic between a visitor's browser and your server while also proving the site is genuinely who it claims to be. A certificate that has expired, is misconfigured, or does not match the domain it is served on will trigger browser warnings that drive visitors away. This tool checks a domain's current certificate, when it expires, who issued it, and whether the chain of trust is set up correctly.
How it works
DNSbyte connects to the domain over HTTPS and retrieves the certificate currently being presented, then verifies several things at once: the certificate's validity period, whether it matches the domain name being checked, the issuing certificate authority, and whether the full certificate chain, including any intermediate certificates, is correctly configured so browsers can verify it without errors.
A certificate can be technically valid but still cause warnings if the chain is incomplete, which is a common cause of "this connection is not private" errors that confuse site owners since the certificate itself has not expired.
Frequently asked questions
My certificate is valid but visitors still see a security warning, why?
The most common cause is an incomplete certificate chain, where the server is not sending the intermediate certificate that links your certificate back to a trusted root authority. Most browsers cannot verify the chain without it, even though the end certificate itself is perfectly valid.
How far in advance should I renew my certificate?
Most providers and automated systems renew somewhere between 30 and 14 days before expiry, giving enough buffer to catch and fix any renewal failures before the certificate actually expires and causes visible warnings to visitors.
What is the difference between domain validation, organisation validation, and extended validation certificates?
Domain validation only confirms you control the domain and is the fastest and most common type today. Organisation and extended validation additionally verify the legal identity of the business behind the certificate, though modern browsers display these largely the same way as domain validation in the address bar, so the practical visual difference to visitors is minimal.
Can I use the same certificate for multiple subdomains?
Yes, either through a wildcard certificate covering all subdomains of a domain, or a multi-domain certificate that explicitly lists each subdomain it covers. A standard single-domain certificate only covers the exact name it was issued for.
My certificate shows as self-signed, is that a problem?
For a public-facing website, yes, since self-signed certificates are not trusted by browsers by default and will always trigger a security warning. Self-signed certificates are normal and fine for internal tools or development environments that are never exposed to the public internet.