How to use Smtp TLS Checker
- Add a PEM certificate to Smtp TLS Checker to get started.
- Press Parse certificate to run it locally in your browser.
- Read the subject, issuer, validity dates and expiry that Smtp TLS Checker lays out for you.
About this tool
Everything Smtp TLS Checker does happens on your own device. Smtp TLS Checker decodes a pasted PEM certificate by walking its ASN.1/DER structure locally to read subject, issuer, validity window and serial.
To check a live site, export its certificate from the browser padlock as PEM and paste it here. Your input never leaves the page, and no account or install is required.
Frequently asked questions
How do I use Smtp TLS Checker?
Use Smtp TLS Checker to check your input without installing anything; everything happens client-side.
Do I need an account for Smtp TLS Checker?
No — Smtp TLS Checker needs no account, sign-up or installation.
Where is my data processed by Smtp TLS Checker?
Entirely in your browser — Smtp TLS Checker keeps your data on your own machine and sends nothing anywhere.
How do I inspect a live site's certificate in Smtp TLS Checker?
Export the certificate from your browser's padlock as PEM and paste it into Smtp TLS Checker; it decodes the ASN.1/DER fields entirely on your device.
Does Smtp TLS Checker work on mobile?
Yes — Smtp TLS Checker is just a web page and runs on any modern browser, including phones and tablets.