It is a requirement that developers install the chrome plugin to validate the GTM code:

It is recommended to set chrome plugin to “Detailed” mode, rather than “Basic” mode:



Here is an example of the Chrome validator in action:image088


Clicking on the “not working” shows details:


Tip: JSON validator is really good for checking the dataLayer for example


“variableName”: “textValue”,

“variableName”: “textValue”


Note: does not like HTML comments, and single-quotes need to be changed to double-quotes in order to validate.


Also JSON formatter for chrome can also be used to make JSON easier to read.


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