Monitor SSL certificate expiry dates with Google Sheets & Slack alerts

Description

This n8n workflow illustrates how to monitor and track SSL certificate expiration dates for any domain using the SSL Checker node from customJS. It automatically updates a Google Sheet with the number of days left until expiry and sends a Slack notification when certificates are about to expire.

What this workflow does

Input** a list of domains from Google Sheets.
Check** each domain’s SSL certificate details, including expiration date and days left.
Update** the Google Sheet with the latest SSL expiry information.
Notify** via Slack if any certificate is expiring soon (e.g., less than 8 days).

Requirements

CustomJS API key** for SSL checking.
Google Sheets API credentials** for reading/updating domain data.
Slack API credentials** (optional, for notifications).

Workflow Steps

Schedule Trigger
⏰ Starts the workflow automatically (weekly by default, configurable).

Google Sheets (Read Rows)
📄 Retrieves the list of domains from your Google Sheet.

CustomJS - Check SSL
🔐 Fetches SSL certificate details for each domain.
Returns JSON output with fields such as expires and daysLeft.

Google Sheets (Update Rows)
📝 Updates the sheet with the current number of days left until certificate expiry.

Check Days Left Threshold (formerly "If" node)
⚠️ Evaluates whether the certificate expires within the threshold (e.g., < 8 days).

Slack Node
💬 Sends a notification message if a certificate is close to expiration.

Example Slack alert message:

⏰ Reminder: SSL certificate of www.example.com
will expire in 7 days.
SSL Checker node JSON output

{
"output": {
"domain": "example.com",
"valid": true,
"expires": "2025-12-31T23:59:59.000Z",
"issuer": "Let's Encrypt",
"daysLeft": 5
}
}