SSL / TLS Certificate Checker
Verify HTTPS certificates, validity periods, issuing Certificate Authority (CA), and TLS negotiation from a remote probe.
Best solution
Network diagnostic: SSL / TLS Certificate Checker; Subject Common Name & Issuing CA.
No measurement yet. This checks from Globalping probes, not from your computer. No continuous monitoring.
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Methodology & calculation rule
Performs TLS 1.2/1.3 cryptographic handshake negotiation, parsing the X.509 server certificate chain and expiration timestamps.
Network observations execute bounded requests to public measurement backends (ipify, Google Public DNS, Globalping, or Cloudflare). Measurements distinguish local client configuration from external internet reachability.
No browsing history, private tokens, or credentials are captured. Results are snapshots of external probe vantage points at the recorded observation timestamp.
Real-World Context & Technical Standards
Public Key Infrastructure (PKI) Certificates
X.509 v3 certificates bind public cryptographic keys to domain names (Subject Alternative Names / SAN), allowing TLS clients to verify server authenticity and encrypt symmetric session keys.
The CA/Browser Forum 398-Day Ceiling
Modern web standards enforce a maximum TLS certificate validity period of 398 days (with industry proposals driving toward 90 days), mandating automated ACME renewal protocols (such as Let's Encrypt).
Server Name Indication (SNI)
SNI transmits the requested hostname in the TLS Client Hello handshake, enabling web servers and CDNs to host thousands of distinct HTTPS domains and SSL certificates on a single shared IP address.
Related network diagnostic tools
| Tool | Metric | Scope |
|---|---|---|
| What Is My IP Address? | Diagnostic | what is my ip address |
| IP Address Lookup | Diagnostic | ip address lookup |
| Remote Ping Test | Diagnostic | ping test |
| DNS Lookup | Diagnostic | dns lookup |
| Is It Down? | Diagnostic | is it down |
Frequently Asked Questions
Why is my SSL certificate showing as untrusted?
Certificates can fail trust validation due to expiration, hostname mismatches (SAN missing), self-signed root authorities, or an incomplete intermediate CA certificate chain on the server.
How many days before expiration should a TLS certificate be renewed?
Automated certificate managers (such as Let’s Encrypt Certbot) renew certificates 30 days prior to their 90-day expiration to prevent accidental downtime.