Monitor SSL certificate expiry with Google Sheets and SMTP email alerts

Who is this for?

DevOps engineers, sysadmins, and website owners who manage multiple domains and need proactive SSL certificate expiration monitoring without manual checks.

What it does

Automatically monitors SSL certificates across multiple domains, tracks expiration status in a Google Sheet dashboard, and sends beautifully formatted HTML email alerts before certificates expire.

✅ No API rate limits — Uses direct OpenSSL commands, so you can scan unlimited domains with zero API costs or restrictions.

How it works

- Triggers on schedule (every 3 days at 10AM) - Reads domain list from your Google Sheet - Checks each domain's SSL certificate using OpenSSL commands - Parses expiration dates, issuer info, and calculates days remaining - Updates Google Sheet with current status for all domains - Sends styled email alerts only when certificates are expiring soon

Set up steps