URL contains more than one Google Tag Manager code
This means that the URL in question contains more than one Google Tag Manager snippet.
Why is this important?
Google Tag Manager (GTM) is user-friendly solution to managing tracking and analytics tags, for example Adwords Conversion Tracking and Google Analytics.
This Hint highlights that more than one GTM snippet was found.
Whilst this is supported by Google, it is not recommended - so this Hint exists to highlight the issue for further investigation.
What does the Hint check?
This Hint will trigger for any internal URL that contains more than one GTM code within scripts on the page.
Examples that trigger this Hint
The Hint would trigger for any URL which contains a script in the <head> that contains a GTM code (e.g. GTM-XXXX);
and contains at least one more script in the <head> that contains a GTM code (e.g. GTM-YYYY);
Why is this Hint marked 'Potential Issue'?
This Hint is a 'Potential Issue', which means that it is unlikely to be affecting the site at the moment, but should be investigated as it could cause issues in the future.
It is entirely possible that you might run into a situation where multiple Google Tag Manager containers are required on the same page. Whilst it is valid, Google advise to keep the number of Google Tag Manager containers on the page minimal, for best performance.