Check a website's SSL certificate
Type a domain. We connect to port 443 from our server and show who issued the certificate, when it expires, how many days are left and whether the name matches. An expired one is a reason to call. Free, no account.
How the check works
- The address is parsed first: http and https only, ports 80 and 443 only, no usernames, no IP addresses and no internal names such as localhost. Anything else is refused before any request.
- The name is resolved and every address it points to must be public. Private, loopback, link-local (cloud metadata included), multicast and reserved addresses are refused, and the connection goes to the address that was checked.
- We open one TLS connection to port 443 of that address, first with the standard checks (trusted issuer, in date, right name). If those fail we connect again without them, only to read the certificate and tell you why it failed. No page is requested.
- The expiry date, issuer, names and key are read from the certificate itself. Days left are counted from the time of the check.
- The whole check has a 6-second budget. It is limited to 10 checks a minute per connection.
Why an expired certificate is a sales lead
- When a certificate has expired, browsers put a warning page between the visitor and the site. A business owner often has no idea until a customer says so.
- It is also an easy thing to prove: the date is in the certificate and anyone can check it. You are pointing at a fact, not a guess.
- Check the site yourself before you write, say what you saw in your own words, and offer to fix it. Do not claim lost sales you cannot know about.
To find businesses to check, search 67Leads by trade and city, or start from businesses whose website is broken. Many sites at once: bulk URL checker.
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Questions
Type the domain above. The expiry date and the days left come from the certificate the server presents on port 443.
The certificate lists other domain names and not this one, for example a certificate bought for the bare domain used on a www address, or a hosting company's default certificate. Browsers show a warning.
No. It reads the leaf certificate and whether the standard checks passed. It does not test revocation or grade the server's TLS settings.
This checks the name you type. If it redirects elsewhere, check the redirect with the redirect checker and the final domain here.
No. One live connection per check; the address and the result are not saved, cached or indexed.
No. It fills templates with what you type and makes no network calls.
No. The result is written when the page is served and not saved.
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