No. The checker only reads the public certificate a server presents during a TLS handshake, which never includes the private key.
Free SSL Tool
SSL Certificate Checker, CSR Generator & Decoder
Check any domain's live SSL certificate, generate a private key and CSR for a new certificate order, or decode an existing certificate or CSR to see exactly what's inside it.
- ✔ Live certificate check
- ✔ CSR & private key generator
- ✔ Keys generated in your browser
- ✔ Free Forever
Everything You Need to Manage SSL Certificates
SSL/TLS certificates power the padlock in every browser address bar, and getting them wrong — an expired certificate, a missing intermediate, or a malformed CSR — causes real outages and trust warnings for visitors.
This free toolkit covers the three things site owners and developers need most: checking a live domain's installed certificate, generating a private key and CSR to submit to a Certificate Authority, and decoding an existing certificate or CSR to inspect exactly what it contains.
How It Works
1. Checker
Enter a domain and we connect to it directly to read its live, currently-installed certificate.
2. Generator
Fill in your organization details and we build a private key and CSR entirely in your browser.
3. Decoder
Paste any certificate or CSR to see its subject, validity, SANs, and other fields decoded.
This check connects directly to the domain on port 443 from our server to read its
live, currently-installed certificate — it is not a client-side lookup, so the page
reloads to show results.
Certificate for systron.net
| Subject (CN) | systron.net |
| Issuer | Let's Encrypt |
| Valid From | 08 Jul 2026 |
| Valid To | 06 Oct 2026 — 51 day(s) remaining |
| Signature Algorithm | RSA-SHA256 |
| Serial Number | 05422F28F84D385178B82AD8D1E47977AB21 |
| Chain Length | 4 certificate(s) presented |
| Subject Alt Names | systron.net www.systron.net |
The private key is generated locally in your browser and is never transmitted
anywhere. Save it immediately and keep it secret — it's required to install the
certificate your Certificate Authority issues from this CSR.
SSL Fundamentals
SSL Checker vs CSR vs Decoder — What's the Difference?
Checker
Inspects the certificate a live website is currently presenting — useful for confirming expiry, chain, and SANs on a domain you don't control the server for.
CSR Generator
Creates a new private key and Certificate Signing Request before you own a certificate — the first step when ordering one from a CA.
Decoder
Reads the fields out of a certificate or CSR you already have in text form — no network connection involved at all.
FAQsSSL Checker, CSR & Decoder
Does the SSL Checker see my private key?
Is the CSR Generator's private key sent to your server?
No. The private key is generated and stays entirely inside your browser using JavaScript. Only the CSR, which contains no secret material, is meant to be shared with a Certificate Authority.
Why did the SSL Checker page reload instead of showing results instantly?
Checking a live certificate requires a real server-side connection to the target domain, which this tool performs safely via a standard form submission rather than background scripting.
Can I decode a certificate without an internet connection?
Yes. The decoder parses the pasted text entirely in your browser and makes no network requests.