UTM parameters
Also called: utm codes, utm tags, urchin tracking module
UTM parameters are tags added to a URL's query string (utm_source, utm_medium, utm_campaign, plus optional utm_term and utm_content) that tell analytics tools like GA4 where a click came from and which campaign drove it, so you can attribute traffic to specific sources.
The five standard tags
Three tags matter most for clean reporting: utm_source (where the click came from, e.g. newsletter), utm_medium (the channel type, e.g. email or cpc), and utm_campaign (the specific push, e.g. spring_sale). Two are optional: utm_term (the paid keyword) and utm_content (which creative or link variant was clicked). GA4 also reads newer tags like utm_id and utm_source_platform. Anything you leave off shows up as (not set) in reports.
Values are case sensitive, so utm_source=Google and utm_source=google become two separate rows. Pick one lowercase convention and stick to it, or your channel data fragments.
You build the URL by appending the pairs after a ?, joined with &:
https://example.com/page/?utm_source=newsletter&utm_medium=email&utm_campaign=spring_saleGA4 uses these to populate the Traffic acquisition report, grouping sessions by source, medium, and campaign so you can see which efforts actually drove visits and conversions.
The name is a holdover. UTM stands for Urchin Tracking Module, after Urchin, the analytics company Google bought and turned into Google Analytics. The tags were already an industry standard, so Google kept the prefix.
How it affects your traffic
UTMs are a marketing tool, but they cause SEO problems when misused, and that is where an audit earns its keep. Never put UTM tags on internal links: each internal click starts a fresh session and overwrites the original source, so your organic and referral numbers get diluted. Worse, when UTM-tagged URLs get crawled and indexed, Google sees near-duplicate pages competing with your clean canonical, wasting crawl budget and splitting link signals. An SEO Audit flags indexed parameter URLs, missing canonical tags, and internal links carrying UTMs before they distort both your rankings and your analytics.
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