zvera
FREE SSL/TLS DIAGNOSTICWebsite Tools

SSL Certificate Checker & Expiry Tracker

Validate HTTPS security certificates in real time. Inspect issuer details, expiration countdown, Subject Alternative Names (SANs), cipher suites, and hostname matching.

Quick Definition

An SSL/TLS certificate encrypts communication between a user's web browser and the web server. An SSL checker verifies that the certificate was issued by a trusted Certificate Authority (CA), has not expired, matches the visited domain, and negotiates modern secure cipher suites.

SSL / TLS Certificate Inspector

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PROACTIVE EXPIRY ALERTING

Get notified before your SSL certificate expires

Don't let an expired certificate take down your web presence. Uzvera automatically checks your production certificates every hour and notifies your engineering team weeks before expiration.

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SECURITY ARCHITECTURE

Complete Guide to SSL/TLS Certificates

How transport encryption safeguards web traffic and how administrators avoid costly certificate outages.

How SSL/TLS Certificates Protect Web Traffic

Transport Layer Security (TLS)—still colloquially called SSL—is the fundamental protocol that encrypts traffic between web browsers and servers. When a user connects to an HTTPS URL, the browser initiates a cryptographic handshake:

  1. Client Hello: The browser transmits supported TLS versions and cipher suites.
  2. Server Hello & Certificate: The server presents its digital certificate containing its public key and signed by a trusted Certificate Authority (CA).
  3. Trust Validation: The browser verifies that the certificate was signed by a trusted root in the OS or browser trust store (e.g. Let's Encrypt, DigiCert) and has not expired.
  4. Session Key Negotiation: Using asymmetric cryptography (ECDHE), the client and server negotiate a shared symmetric session key (e.g. AES-256-GCM) for ultra-fast encrypted data transfer.

The Hidden Cost of Expired Certificates

Certificate expiration is one of the most common causes of preventable web outages among high-profile companies. Modern browser security models intentionally treat expired certificates as a hard failure:

  • Immediate Traffic Halt: Major browsers display blocking warning screens that scare off over 90% of non-technical visitors.
  • API Integrations Severed: Automated curl commands, mobile apps, and payment gateway webhooks will immediately abort connections when SSL validation fails.
  • SEO Rankings Impact: Search engines like Google down-rank websites that consistently throw SSL errors or fail uptime checks.

The 90-Day Industry Standard: While certificates used to be issued for 2 to 5 years, modern industry guidelines have capped maximum validity to 398 days, and Let's Encrypt issues certificates valid for only 90 days. This makes automated continuous expiration monitoring essential.

Common SSL Certificate Errors and How to Resolve Them

When a certificate fails this checker or throws browser warnings, check these frequent culprits:

  1. Hostname Mismatch (ERR_CERT_COMMON_NAME_INVALID): The requested domain is missing from the Subject Alternative Names (SANs) list. Reissue the certificate ensuring all domain variations (e.g. both domain.com and www.domain.com) are included.
  2. Incomplete Certificate Chain: The web server is serving only the leaf certificate and omitting the intermediate CA certificate. Browsers on desktop may cache the intermediate, but mobile browsers will fail. Always configure the full-chain file (e.g. fullchain.pem in Nginx).
  3. Outdated TLS Protocols (TLS 1.0 / 1.1): Legacy protocols and CBC ciphers are disabled by modern browsers. Ensure your web server configuration restricts handshakes to TLS 1.2 and TLS 1.3.
COMMON QUESTIONS

Frequently Asked Questions: SSL Certificates

Key information regarding HTTPS encryption, renewal timelines, and certificate validation.

What happens when an SSL/TLS certificate expires?

When an SSL certificate expires, web browsers immediately block access with severe full-screen security warnings (such as 'Your connection is not private' or 'NET::ERR_CERT_DATE_INVALID'). Users cannot safely access your website, conversion rates drop to zero, search engine rankings can be penalized, and automated APIs communicating with your backend will fail.

How far in advance should an SSL certificate be renewed?

Industry best practice is to renew certificates at least 14 to 30 days before expiration. Automated tools like Let's Encrypt (Certbot) typically renew certificates at the 60-day mark of their 90-day lifespan, leaving ample time to identify and resolve renewal or DNS validation issues before an outage occurs.

What is an SSL hostname mismatch error?

A hostname mismatch (ERR_CERT_COMMON_NAME_INVALID) happens when the domain in the browser's address bar does not match any name listed in the certificate's Common Name (CN) or Subject Alternative Names (SANs). For example, if a certificate covers 'example.com' but you access 'app.example.com' without a wildcard or specific SAN entry, browsers will trigger a security warning.

What is a Subject Alternative Name (SAN) certificate?

A SAN certificate (often called a Multi-Domain or Unified Communications certificate) protects multiple distinct domain names, subdomains, or IP addresses under a single cryptographic certificate. For instance, one certificate might protect 'uzvera.com', 'api.uzvera.com', and 'app.uzvera.com'.

What is the difference between TLS 1.2 and TLS 1.3?

TLS 1.3 is the modern cryptographic standard designed to be faster and significantly more secure than TLS 1.2. It cuts the initial handshake time in half (reducing round-trips from two to one), supports Zero Round Trip Time (0-RTT) resumption, and eliminates obsolete, vulnerable cryptographic algorithms (such as RC4, DES, and SHA-1).

Can Uzvera notify me automatically before my certificate expires?

Yes. Uzvera includes automated 24/7 background SSL and website uptime monitoring. You can configure alerts to trigger 30, 14, and 3 days before any production certificate expires, sending instant notifications via email, webhooks, or push notifications.

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