# SSL/TLS certificate checker

Check any site's SSL/TLS certificate, its issuer, and how many days until it expires.

Enter a domain and we open a live TLS connection to it, read the certificate it serves, and tell you plainly whether HTTPS is healthy and when the certificate expires.

## What we check

- That the site answers over HTTPS with a valid, trusted certificate.
- Who issued the certificate and which protocol was negotiated (for example TLS 1.3).
- When the certificate becomes valid and when it expires, with a days-remaining countdown.
- Which hostnames the certificate covers, plus its serial and SHA-256 fingerprint.

## Why it matters

An expired or missing certificate is one of the fastest ways to take a site offline: browsers replace the page with a full-screen security warning and turn visitors away. Certificates also expire quietly, often every 90 days, so the failure tends to arrive at the worst possible moment. Knowing the expiry date ahead of time turns an outage into a calendar reminder.

## Frequently asked questions

### What does this SSL/TLS checker actually do?

It opens a real TLS connection to the domain on port 443, reads the certificate the server presents, and parses its issuer, validity window, covered hostnames, and fingerprint. Nothing is stored.

### How long before expiry should I renew?

Renew well before the certificate lapses. We flag a certificate as urgent within 14 days of expiry and worth watching within 30. The reliable fix is automated renewal so it never comes down to a manual deadline.

### My certificate is valid but the site still shows a warning. Why?

Common causes are a certificate that does not cover the exact hostname you visited (for example the bare domain versus www), a missing intermediate certificate in the chain, or mixed content loading over plain HTTP. This tool reports the covered hostnames so you can check the first case.

### Can Ranetrace watch this for me?

Yes. This page is a one-time snapshot. Ranetrace re-checks your certificate around the clock and warns you before it expires, so you are never surprised by an outage.

## Run this check

Run it on your own domain here: https://ranetrace.com/tools/ssl-checker

## Related tools

- [DNS lookup](https://ranetrace.com/tools/dns-lookup.md)
- [Domain & WHOIS lookup](https://ranetrace.com/tools/domain-lookup.md)
- [HTTP status & speed check](https://ranetrace.com/tools/http-status.md)

This page is a one-time snapshot. Ranetrace monitors this continuously and warns you before it becomes a problem: https://ranetrace.com/pricing.md