How to use TLS Checker
- Add a PEM certificate to TLS Checker to get started.
- Press Parse certificate to run it locally in your browser.
- Use the subject, issuer, validity dates and expiry TLS Checker produces — nothing was uploaded.
About this tool
TLS Checker is a static, client-side tool with no backend. Paste a PEM certificate and TLS Checker parses the X.509 fields entirely on your device.
The expiry countdown is computed locally, and nothing about the certificate is transmitted. Nothing you enter is uploaded, and it keeps working offline once the page has loaded.
Frequently asked questions
How do I use TLS Checker?
Use TLS Checker to check your input without installing anything; everything happens client-side.
Do I need an account for TLS Checker?
No — TLS Checker needs no account, sign-up or installation.
Does TLS Checker upload my data?
No — TLS Checker processes everything locally in your browser, so nothing you enter is uploaded or stored.
How do I inspect a live site's certificate in TLS Checker?
Export the certificate from your browser's padlock as PEM and paste it into TLS Checker; it decodes the ASN.1/DER fields entirely on your device.
Does TLS Checker work offline?
Once the page has loaded, TLS Checker keeps working with no network connection.