Why Isn't My Tag Firing?
A tag that doesn’t fire has a specific cause. It is not random. Work through the flowchart below systematically — every non-firing tag falls into one of these categories.
Walkthrough by symptom
Section titled “Walkthrough by symptom”If the flowchart didn’t resolve your issue, here are the 12 most common causes with direct solutions:
1. Container not on the page
Section titled “1. Container not on the page”Run in console: typeof window.google_tag_manager. If it returns "undefined", the container isn’t loaded. Check your installation.
2. Container loaded but not published
Section titled “2. Container loaded but not published”Check the version number in the console:
Object.keys(window.google_tag_manager).filter(function(k) { return k.startsWith('GTM-'); })The published version is what users see. Preview mode shows your workspace changes.
3. Event name typo
Section titled “3. Event name typo”In Preview mode, click your custom event in the timeline. The event name shown must exactly match your trigger’s event name condition. form_submission ≠ form_Submit.
4. Trigger condition not matching actual variable value
Section titled “4. Trigger condition not matching actual variable value”Click your failing tag → Triggers tab → find the red condition → note the actual value → compare it to what you expected. Fix either the data or the trigger condition.
5. Blocking trigger active
Section titled “5. Blocking trigger active”In the Tags panel, if a tag shows “Blocked by Exception,” find the exception trigger and check why it’s evaluating to true.
6. Consent mode blocking
Section titled “6. Consent mode blocking”In the Timeline, check whether a consent update event appeared. If consent is denied, tags configured with consent requirements won’t fire.
7. Tag paused
Section titled “7. Tag paused”A pause icon on the tag in GTM means it won’t fire regardless of triggers.
8. Tag firing but script error prevents it from running
Section titled “8. Tag firing but script error prevents it from running”The tag fires (blue in Preview mode) but throws an error. Check the Errors tab for JavaScript errors in Custom HTML tags.
9. Ad blocker preventing tag execution
Section titled “9. Ad blocker preventing tag execution”Test in a clean incognito window with no extensions. If the tag fires there but not in your normal browser, an extension is the cause.
10. CSP blocking the script
Section titled “10. CSP blocking the script”Check the browser console for Content-Security-Policy errors. The required domains need to be in your allowlist.
11. Tag sequencing failure
Section titled “11. Tag sequencing failure”If this tag depends on a Setup Tag, and the Setup Tag failed, this tag won’t fire. Check the Setup Tag status in Preview mode.
12. Data is in GA4 but not visible in reports
Section titled “12. Data is in GA4 but not visible in reports”Wait 24-48 hours. Check GA4 → Configure → Events to see if the event is registered. Check for active data filters in Admin → Data Filters.