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
- Connect your Google Sheets OAuth2 credentials
- Create a Google Sheet with these columns: **Domain**, **Expiry Date**, **Days Left**, **Status**, **Issuer**, **Last Checked** (the workflow matches on the Domain column to update results)
- Add your domains to scan in the **Domain** column
- Update the Sheet ID in the **Read Domain List from Google Sheets** and **Update Google Sheet with Results** nodes
- Connect SMTP credentials in the **Send Alert Email via SMTP** node
- Optionally adjust `ALERT_THRESHOLD_DAYS` in two nodes: **Prepare Domain List and Set Threshold** and **Parse SSL Results and Identify Expiring Certs** (default: 20 days)
Setup time: ~10 minutes
