n8n Workflow: Monitor Uptime & Visual Drift to Slack

Get instant Slack alerts when your website goes down—or when it visually drifts

This n8n workflow monitors a list of URLs from your Google Sheets every 10 minutes using Snapshot Site for uptime and visual comparisons, then posts Slack alerts only when a page’s state changes (up, down, or visual drift). It also writes the latest state back to the sheet for reliable tracking.

What this workflow does

• Runs on a schedule every 10 minutes via an n8n scheduling trigger.
• Reads your Google Sheets “Watchlist” tab and processes each row one URL at a time.
• Uses Snapshot Site Analyze (with quality checks) to determine whether each page is up or down, capturing a reason and screenshot link.
• If the page is up, uses Snapshot Site Compare to compare the live page against your baselineUrl and flags visual drift when the mismatch percentage crosses your threshold.
• Compares the newly computed state to lastState from Google Sheets and formats a Slack message only when a state transition occurs (including recoveries).
• Posts the alert to Slack and then updates Google Sheets with lastState and lastCheckedAt.

Use cases

• Track the uptime of key customer-facing pages and recoveries with low noise Slack notifications.
• Detect “looks different” issues after deployments by monitoring visual drift against baseline screenshots.
• Maintain an auditable page health history in Google Sheets with last state timestamps.

Technical details

• Google Sheets: reads the Watchlist tab and updates lastState and lastCheckedAt.
• Snapshot Site: uses Snapshot Site Analyze (quality checks) and Snapshot Site Compare for visual drift detection.
• Slack: sends alerts only when a state changes.
• n8n nodes mentioned in this workflow: if, set, code, no op, slack, and sticky note.