UTM Parameters
UTM parameters are standardised additions to a URL (utm_source, utm_medium, utm_campaign, plus the optional utm_id, utm_term and utm_content) that manually label where a website visit came from. In GA4 they feed into channel attribution, allowing fine-grained analysis of individual campaigns, newsletters or partnerships independently of automatic channel grouping.
In practice
In practice, UTM parameters are set mainly on links outside your own domain – in newsletters, social media posts or paid partnerships – while internal links and Google Ads clicks usually pass their origin automatically. What matters is a naming convention that applies across the whole company, keeping every value lowercase for example, because GA4 treats utm_source=Newsletter and utm_source=newsletter as two separate sources. Without clear conventions, reports quickly fragment into far more rows than anyone needs. Alongside the five classic parameters, Google also lists utm_id, utm_source_platform, utm_creative_format and utm_marketing_tactic; utm_id matters most in practice, because GA4 evaluates this campaign ID.