UTM codes are parameters that are added to the end of a URL to track the performance of a marketing campaign. UTM codes, which stand for "Urchin Tracking Module" codes, were developed by Google to track the source and effectiveness of marketing campaigns that use URLs.
UTM codes are typically added to the end of a URL as a series of name-value pairs, separated by ampersands (&).
For example, consider the following URL:
https://www.example.com/?utm_source=google&utm_medium=cpc&utm_campaign=spring_sale
In this URL, the utm_source, utm_medium, and utm_campaign parameters are UTM codes. The utm_source parameter specifies the source of the traffic (e.g., Google), the utm_medium parameter specifies the medium through which the traffic was generated (e.g., paid search), and the utm_campaign parameter specifies the marketing campaign that the traffic is associated with (e.g., spring sale).