Help Centre
Everything you need to get the most out of Certline: how to check a certificate, what each result means, and what the tool does — and doesn’t — do.
Getting started
Certline is a free, stateless tool. There is no account, no sign-up, and nothing to install.
- Open the app.
- Type the bare hostname you want to check — for example
example.com, with nohttps://and no path. - Click Check. Certline opens a real TLS connection to that hostname on port 443, reads the certificate the server actually presents, and shows the report.
The check may take a few seconds depending on network conditions. The report shows the expiry date and days remaining, the issuer and subject, every hostname the certificate covers (the SANs), whether the intermediate chain is complete, the TLS version, the fingerprint, and the serial number.
Frequently asked questions
How do I check a certificate?
Go to the app, enter a hostname, and click Check. Certline connects to that exact hostname on port 443 and reports the certificate it receives. No account or API key is needed.
What does “chain incomplete” mean?
The server sent its leaf certificate but did not send the intermediate certificate that links it to a trusted root. Your certificate can be perfectly valid and your site can still break for visitors, because desktop browsers often paper over a missing intermediate from their cache while mobile clients do not. This is the failure that is invisible to anyone looking only at the expiry date. If Certline reports the chain as incomplete, check your web server configuration and make sure it is serving the intermediate certificate alongside the leaf.
Does Certline save my hostname searches?
No. Certline is stateless. The hostname you enter is used to open the TLS connection and is discarded as soon as the check completes. There is no account, no history, and the server does not log or store hostnames, IP addresses, or certificate data beyond the duration of the request.
Why did my check fail with an error?
An error means the check did not complete — it does not necessarily say anything about your certificate. The most common causes are a hostname that does not resolve, a server that is not listening on port 443, or a connection that timed out. When a check fails, Certline says plainly that the check did not complete and why. If the server could not be reached at all, re-check the hostname spelling and confirm the service is actually up on port 443 before assuming the certificate itself is at fault.
Can I check multiple hostnames at once?
No. Certline checks exactly one hostname per request, and it checks only the hostname you type. It does not scan ranges and does not enumerate subdomains. If you manage several servers, run a check for each hostname you care about.
Can Certline email me when my certificate is about to expire?
No, and Certline never will until an email sender is connected. There is no email alerting, no scheduled re-check, and no reminder service. Certline answers when you ask it — it does not watch certificates in the background. If you need expiry monitoring, keep that in mind for whichever other tooling you use; Certline is a point-in-time checker, not a monitoring service.
Known limitations
Certline is honest about what it does and does not do. These are current limitations, not planned promises.
No email alerts, reminders, or scheduled re-checks
There is no email sender connected to this service. Certline cannot notify you when a certificate is about to expire and does not perform background monitoring. It only reports when you run a check.
One hostname at a time, port 443 only
Certline checks a single hostname per request on port 443. It does not scan IP ranges, enumerate subdomains, or check non-standard ports.
No chain trust validation
Certline reports the chain the server sends and whether it is complete, but it does not validate the certificate against a public trust store or claim compliance with any standard, certification, or audit regime. Treat the report as informational.
Self-hosted deployment is planned, not available
A self-hosted option is under consideration but cannot be purchased today. No payment information is collected, and no payment processor is connected. Until the owner connects one, every checkout on this site is a demonstration only.
Contacting us
Support is not reachable by email yet — no mailbox is connected to this site, so an email address would not reach anyone. Until the owner connects a support channel, the best place for product questions is the information on this page. We have flagged the need for a real support contact with the site owner.
Last updated: 5 August 2026