The Google Tag Assistant extension for Chrome allows you to check for the presence of several different types of Google code snippets, or “tags”, on a Web page.
After the free and easy install, you can click the tag icon in the Chrome extension bar to display information about the Google Analytics code on the page, including the UA number, which identifies the Google Analytics property to which all raw website data is sent. It also offers suggestions, such as placing the Google Analytics tracking code within thetags (which is recommended but not completely necessary for Google Analytics to execute correctly).
Interestingly, Google Tag Assistant also displays the container ID of Google Tag Manager container if this code is also present and indicates the UA number of any Google Analytics tags that you have deployed to the page through Google Tag Manager. (Remember not to confuse Google Tag Assistant with Google Tag Manager.)
One issue that Google Tag Assistant sometimes calls out is the occurrence of multiple Google Analytics UA numbers on a single Web page. It may be perfectly valid to have two different tracking codes with two UA numbers on a single page (for rollup reporting), but multiple tracking codes sometimes indicate a need for tighter management of the Google Analytics deployment.
Keep in mind that you do not need to be logged into Google Analytics or Google Tag Manager to use Google Tag Assistant, and that you can activate it to display Google tag information for any page on any website, not just your own.