The most commonly used parameters in custom tracking URLs include:
utm_source: Identifies the source of the traffic, e.g., newsletter, social media, etc. utm_medium: Specifies the medium, e.g., email, CPC, banner, etc. utm_campaign: Defines the specific campaign name or identifier. utm_term: Used for paid search to identify keywords. utm_content: Differentiates similar content or links within the same email.