UTM parameters are short tags added to the end of a link, such as ?utm_source=instagram&utm_medium=social, that tell Google Analytics and similar tools where a visit came from.
Clicks from an Instagram bio, a story, a newsletter or an app often arrive with no referrer, so analytics shows them as "direct" and you can't tell which post brought the visitor. UTM parameters label the link itself.
Google's guidance is to always set utm_source, utm_medium, utm_campaign; content and term are optional, and help tell apart two links in one campaign. Keep the values lowercase and consistent, because "Instagram" and "instagram" are counted as two sources.
A photographer puts a link in her Instagram bio ending ?utm_source=instagram&utm_medium=social&utm_campaign=autumn_minis.
A week later Google Analytics shows 64 visits from that campaign and three bookings, which she would otherwise have seen as anonymous direct visits.
Related terms