SSL Certificate Validation API — Check Any Domain in Seconds
Retrieve and validate SSL/TLS certificate details for any domain. Get issuer information, validity period, encryption standard, and chain of trust — all in structured JSON or XML via a single API call.
Try the SSL Certificate API
Enter a domain name to retrieve its SSL certificate details in real time.
Complete SSL Intelligence in One Call
Every API response includes everything you need to assess the security posture of a domain's SSL/TLS configuration.
Validity Status
Instantly know if a certificate is valid, expired, or misconfigured. Boolean flag plus detailed status reason.
Issuer Details
Certificate Authority name, organization, and country. Identify Let's Encrypt, DigiCert, Sectigo, and more.
Validity Period
Exact issuance and expiration dates. Calculate remaining days and plan renewals before downtime occurs.
Chain & Encryption
Serial number, subject CN, encryption standard, and full certificate chain information for deep validation.
Why Developers Use Our SSL API
Expiry Monitoring & Alerting
Check certificate expiration dates across your entire infrastructure. Combine with our Domain Monitoring service to get automatic alerts before a certificate expires and causes downtime.
Security Auditing & Compliance
Verify that certificates meet your organization's security standards. Check encryption strength, issuer trust, and proper configuration for PCI-DSS, SOC 2, and other compliance frameworks.
DevOps & CI/CD Integration
Add certificate checks to your deployment pipeline. Verify SSL is correctly provisioned after deploying a new service. Cross-reference with DNS records to ensure domains resolve to the right endpoints.
Phishing & Threat Detection
Analyze SSL certificates of suspicious domains. Cross-reference certificate data with WHOIS registration details to identify phishing sites, typosquatting, and fraudulent certificates.
One Endpoint, Full SSL Data
A single GET request returns everything. Use the same API key and authentication header as all other WhoisJSON endpoints.
Authentication: Authorization: TOKEN=YOUR_API_KEY
Format: JSON (default) or XML with format=xml
{
"domain": "google.com",
"valid": true,
"valid_from": "2024-10-21T08:24:36.000Z",
"valid_to": "2025-01-13T08:24:35.000Z",
"issuer": {
"C": "US",
"O": "Google Trust Services",
"CN": "WR2"
},
"details": {
"subject": {
"CN": "*.google.com"
},
"serialNumber": "..."
}
}
What Is an SSL Certificate API?
An SSL certificate API allows developers to programmatically validate and inspect SSL/TLS certificates for any domain. Instead of manually checking certificates in a browser, you can automate the process — verifying issuer trust, checking expiration dates, inspecting encryption standards, and monitoring certificate changes at scale. WhoisJSON's SSL Certificate API returns structured JSON or XML data for every domain you query, making it easy to integrate into monitoring dashboards, security tools, and compliance workflows.
Part of the WhoisJSON Unified Platform
The SSL Certificate API is one of six endpoints on the WhoisJSON platform. The same API key that powers your SSL checks also gives you access to WHOIS lookups, DNS record resolution, domain availability checks, subdomain discovery, and automated domain monitoring. This unified approach means you can cross-reference SSL data with WHOIS registration details and DNS configurations in a single workflow — no juggling multiple providers or API keys.
Scale from Side-Projects to Enterprise
The free plan includes 1,000 API requests per month shared across all endpoints — enough for small projects and testing. When you need more, our paid plans scale up to unlimited requests with rate limits of 300 requests per minute and enterprise-grade SLAs. Read the full API documentation or check our FAQ to get started.
Start Validating SSL Certificates Today
Create your free account and check your first SSL certificate in under a minute.