Getting started with Certline, answers to common questions, and what this tool can and cannot do.
Using Certline takes about ten seconds:
example.com — no https:// prefix, no path).Certline opens a TLS connection to that host on port 443, reads the certificate the server actually presents, and reports the expiry date and days remaining, who issued it, every hostname the certificate covers (SANs), and whether the server sent its intermediate certificate (chain completeness).
No account, no sign-up, no email required. One request, one response.
A certificate being unexpired does not guarantee the site loads. The most common hidden failure is a missing intermediate certificate. The server sends the leaf certificate but not the intermediate authority — desktop browsers may paper over this from cache, but mobile browsers and API clients cannot reach your site. Check the "Chain complete" field in Certline's results. If it shows No, that is the likely cause.
No. A connection failure means Certline could not complete the TLS handshake. The cause could be a mistyped hostname, DNS not resolving, the server being offline, a firewall blocking port 443, or the server not supporting TLS. Certline reports connection failures as what they are — failures to connect — not as findings about your certificate. Check the hostname and try again. If the host is behind Cloudflare, the check will see the edge certificate Cloudflare presents, not your origin server's certificate.
No. Certline checks one hostname at a time. It does not scan IP ranges, enumerate subdomains, accept comma-separated lists, or process uploaded files. This is by design — the tool gives a thorough single-host result, not a shallow scan.
No. Certline checks the hostname you provide at the moment you provide it and returns one result. There are no scheduled re-checks, no email alerts, no reminders, and no monitoring dashboard. There is no email sender in this fleet. One request, one response. If you need proactive monitoring, you will need to use a dedicated monitoring service.
Chain depth is the number of certificates the server sent during the TLS handshake. A depth of 1 means only the leaf certificate was sent — the intermediate was omitted. This is the chain-completeness problem: mobile browsers and API clients that lack the intermediate in their cache will reject the connection. A complete HTTPS chain typically has depth 2 (leaf + intermediate) or depth 3 (leaf + intermediate + root/trust anchor).
Port 443 only — the standard HTTPS port. Certline does not support custom ports such as 8443, 465, or 4433. If you need to check a certificate on a non-standard port, you will need a different tool.
Because Certline has no accounts and stores no data, we cannot investigate issues related to a specific past check. If you see an error or unexpected result, please repeat the check and note the exact hostname, the time, and the error message shown.
For privacy-related questions, see our Privacy page.