In digital advertising, tags are pieces of code (JavaScript, HTML, iframe, etc.) placed on web pages that, when the page loads, request information from or send information to third parties, carry out processes, or specify how something is displayed.

Tags trigger ad calls, sending information to ad servers so appropriate ads can be served, and also collect information about users. Tags can also refer to the keywords that are assigned to digital content so it can be categorised and found through search engines.