GTM preview works but not live: why, and how to fix it
Everything fires in GTM Preview, you breathe a sigh of relief, and then the live site tracks nothing. It’s one of the most common and most confusing GTM problems, and it comes down to a short list of causes.
1. You didn’t publish (the usual one)
Preview mode runs your latest draft workspace, but the live site only runs the published container version. If you made changes and tested in Preview but didn’t hit Submit and Publish, the live site is still running the old version. This is the cause far more often than anything technical.
2. Consent is different for real visitors
In Preview, you’re often interacting with your own consent banner in a way that grants consent, so the tag fires. A real visitor who hasn’t accepted may have the tag held back by consent settings. So it fires for you in Preview and not for them live, which looks like a GTM fault but is actually consent behaving as configured.
Tags fire in Preview but not live?
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Check my tracking free3. Caching and other gremlins
- Caching: a CDN or caching plugin is serving an old page without the latest container. Clear the cache and retest.
- A different container on the live site than the one you edited (test vs live IDs).
- Trigger conditions that happen to be true in your Preview session but not for a typical live visit.
- Blocking triggers or exceptions that quietly stop the tag in live conditions.
How to confirm the fix
After publishing and clearing caches, check the live site in a normal browser using GA4 Realtime or the Meta Pixel Helper, not Preview. Test as a first-time visitor, including the consent path a real user would take. If it fires there, you’re genuinely live, not just live in Preview.
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GTM Preview vs live: common questions
Why does my tag work in GTM Preview but not on the live site?
Most often because you tested a draft in Preview but didn’t publish the container, so the live site runs the old version. Consent behaving differently for real visitors and caching are the other common causes.
Do I need to publish GTM after testing in Preview?
Yes. Preview runs your draft workspace; the live site only runs the published version. Changes don’t go live until you Submit and Publish the container.
Why does a tag fire for me but not for real visitors?
Usually consent. In Preview you often grant consent to your own banner, so the tag fires, while a real visitor who hasn’t accepted has it held back by your consent settings.