How to Check an SSL Certificate for a Hostname

Enter a hostname and optional port, then start the check to view available TLS certificate and connection details. An explicitly empty host returns error data, while an unconvertible port uses 443.

Prepare the host and destination

SSL Checker inspects the TLS certificate presented by a host and reports certificate and connection details available from that attempt. Use it when you need to examine a hostname, check a service on a particular port, or investigate why a TLS connection did not return the information you expected.

The host input is optional and defaults to example.com, while the optional port defaults to 443. A connection attempt allows up to 10 seconds before the TLS handshake is attempted. Depending on the result, you may see certificate subject and issuer information, a serial identifier, negotiated TLS version, cipher information, validity dates, alternate names, and related counts.

Enter the hostname for the endpoint you intend to inspect rather than a broad organization name. Include the port when the service does not use the default. A certificate result describes information obtained from that connection, so read it as the outcome of the selected host and port, not as a broader assessment of the service.

Run the certificate inspection

1. Open SSL Checker and identify the hostname whose TLS certificate you want to inspect.
2. Enter that hostname in the host field. You may omit the field to use the example.com default. Do not submit an explicitly empty host when you expect a certificate check, because an empty host produces error data instead of performing the check.
3. Enter the destination port when it differs from 443. Omitting the port selects 443. Make sure the value can be converted to an integer; if conversion fails, the tool uses 443 rather than the value you intended.
4. Start the check and allow the connection attempt to finish. The tool uses a network connection, waits up to 10 seconds for that connection, and then attempts the TLS handshake.
5. First determine whether a certificate was returned. When certificate details are available, review the subject, issuer, serial identifier, negotiated TLS version, cipher information, validity dates, alternate names, and related counts.
6. If the returned data contains an error, verify the hostname and port before trying again. SSL failures, hostname-resolution failures, refused connections, and other exceptions appear as error data rather than being sent

Read certificate and connection outcomes

A certificate result shows details obtained during the connection. Compare the reported subject and alternate names with the hostname you meant to inspect, then consider the issuer, negotiated TLS version, and cipher information as descriptions of that connection. The serial identifier and related counts provide additional returned certificate information when present.

When certificate dates can be parsed, the result calculates whole-day remaining time and indicates whether the certificate is expired and currently valid. Failed date parsing leaves those derived indicators unavailable rather than calculating them, so their absence does not provide a validity conclusion.

If the TLS connection returns no certificate, the result reports that no certificate was returned. Error data can reflect a resolution failure, refused connection, SSL failure, or another exception. Check the inputs and connection outcome before interpreting missing certificate details as a property of the certificate.

The returned details and derived indicators do not by themselves establish certificate authenticity, standards compliance, security, accuracy, or completeness beyond what the connection supplied.

Worked example

You want to inspect the TLS certificate presented by the hostname target-host on the default port, so you enter that host and run the check.

Enter the descriptive hostname target-host, leave the port at its default, start the check, and inspect whether certificate details, error data, or a no-certificate result is returned.

The returned data may contain certificate subject and issuer details, a serial identifier, negotiated TLS version, cipher information, validity dates, alternate names, and derived validity indicators when dates can be parsed. It may instead contain error data or report that no certificate was返回.

Limitations

• The supplied host and port must produce a usable connection, and the connection attempt can reach its 10-second timeout before the TLS handshake.
• A missing certificate, failed date parsing, TLS failure, resolution failure, refused connection, or other exception can reduce the information returned.

Common errors

• An explicitly empty host returns error data, while a port that cannot be converted to an integer falls back to 443; enter the intended hostname and verify the port before starting.

FAQ

What happens if I leave the host blank?

If the host field is omitted, example.com is used as the default; an explicitly empty host follows a different path and produces error data instead of performing a certificate check.

Which port does SSL Checker use?

Omitting the port selects 443, and a supplied value that cannot be converted to an integer also results in 443; review the entry when the service uses another port.

Does the result show whether a certificate is expired?

Parsed certificate dates provide whole-day remaining time together with expired and currently valid indicators; failed parsing leaves those calculated indicators unavailable in the returned data.