Capture JavaScript Errors with Google Tag Manager and Send to GA4

Objective

To automatically detect and track JavaScript errors on your website using GTM, and send them to Google Analytics 4 as custom events (e.g. js_error), including useful error details.

Step 1: Enable Built-in Error Variables in GTM

1. Go to Google Tag Manager
2. Click Variables in the left menu
3. Click “Configure” (top right)
4. Scroll down to Errors, and enable:

• Error Message
• Error URL
• Error Line
• Error Stack Trace (optional but useful)

Step 2: Create a Trigger for JavaScript Errors

1. Go to Triggers → Click “New”
2. Name the trigger: JS Error – All Pages
3. Trigger Configuration → Select Trigger Type: Error
4. Choose: This trigger fires on All JavaScript Errors
5. Click Save

Step 3: Create the GA4 Event Tag

1. Go to Tags → Click New
2. Name it: GA4 – js_error
3. Tag Configuration → Select Google Analytics: GA4 Event
4. Under Configuration Tag, select your existing GA4 config
5. Event Name: js_error
6. Add Event Parameters (optional but useful for analysis):

Parameter Name	Value
error_message	{{Error Message}}
error_url	{{Error URL}}
error_line	{{Error Line}}

(Optional: Add error_stacktrace with {{Error Stack Trace}})

Step 4: Link the Trigger to the Tag

1. Scroll down to Triggering
2. Choose the trigger: JS Error – All Pages
3. Click Save

Step 5: Preview and Test (Optional)

Testing JavaScript errors is tricky since real errors may not be consistent. You can simulate one manually in the browser console.

Simulate a test error:

1. Open your website
2. Open Developer Console in your browser (F12 or right-click → Inspect → Console)
3. Paste this line and press enter:

setTimeout(function () {

  throw new Error(“Simulated GTM error”);

}, 1000);

1. In the Tag Assistant Preview, check if:

• A js_error event appears
• Your GA4 tag fires with the correct parameters

Step 6: Publish

Once tested and verified:

1. Click Submit → Publish in GTM
2. Name the version: GA4 – JavaScript Error Tracking