GA4 Anomaly Detection with Automated Slack & Email Alerts

Who’s it for

Teams that monitor traffic, signups, or conversions in Google Analytics 4 and want automatic Slack/email alerts when a channel suddenly spikes or drops.

What it does

This n8n template pulls daily GA4 metrics, detects outliers with a rolling mean and z-score, and sends alerts with a sparkline chart. It supports per-channel analysis (e.g., sessionDefaultChannelGroup) and consolidates multiple anomalies into a single email while posting each one to Slack.

How it works

• HTTP Request (GA4 Data API) fetches sessions, newUsers, conversions, bounceRate by date + channel.
• Code calculates 7-day moving average and z-scores, flags anomalies, and builds QuickChart links.
• If filters on alert === true and optional ALERT_ME toggle.
• Slack posts an alert + chart.
• Email sends one summary email (subject + HTML table + charts).

Requirements

• GA4 OAuth2 credential in n8n.
• Slack API credential (bot with chat:write).
• Email credential (SMTP or service).
• GA4 property ID and at least several recent days of data.

Where to find your GA4 Property ID

• In the GA UI:

  1. Open Google Analytics → bottom-left Admin (gear).
  2. In the Property column, click Property settings.
  3. Copy Property ID — it’s a numeric value (e.g., 481356553).

• From the URL (quick way):
  When you’re inside the GA4 property, the URL looks like:
  …/analytics/web/#/p123456789/… → the digits after p are your Property ID (123456789 in this example).

• What not to use:

  • Measurement ID (looks like G-XXXXXXX) — that’s the data stream ID, not the property ID.
  • Universal Analytics IDs (UA-XXXXX-Y) — those are legacy and won’t work with GA4 Data API.

• In this template:
  Put that numeric ID into the Set → PROPERTY_ID field. The HTTP node path properties/{{ $json.PROPERTY_ID }}:runReport expects only the number, no prefixes.

How to set up

1. Open the Set (Define variables) node and fill: PROPERTY_ID, LOOKBACK_DAYS, ALERT_PCT, Z_THRESHOLD, CHANNEL_DIM, ALERT_ME.
2. Connect your Google Analytics OAuth2, Slack, and Email credentials.
3. In Email Send, map Subject → {{$json.emailSubject}} and HTML body → {{$json.emailHtml}}. Keep Execute once enabled.
4. Run the workflow.

How to customize

• Change the moving-average window (WINDOW/MA_WINDOW) and chart range (LAST_N_DAYS_CHART).
• Swap CHANNEL_DIM (e.g., source/medium) to analyze different dimensions.
• Add/remove metrics in the GA4 request and the metrics list in the Code node.
• Tweak thresholds to reduce noise: raise Z_THRESHOLD or ALERT_PCT.

Output example