When I'm trying to preview and debug the marketing pixel tags for my website in Google Tag Manager, I immediately see the message

Preview Confirmation

You are no longer in preview mode for any version of container GTM-XXXX

and I'm unable to preview and debug my site. What is going wrong here?

1 Answer 1


According to this answer in the Google Product Forums, you will get the above message immediately if you have 3rd-party cookies blocked in your browser:

same happend to me until I enabled to accept 3rd partie cookies in firefox!

If you unblock 3rd-party cookies or somehow make an exception rule for Google Tag Manager in your browser, then the preview and debug should work properly.

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