UTM tags (Urchin Tracking Module) are parameters appended to a URL that tell your analytics exactly where a visitor came from and which ad they saw. A plain link like https://mtwspy.com/ tells you nothing; a tagged link like https://mtwspy.com/?utm_source=facebook&utm_medium=cpc&utm_campaign=spring_sale&utm_content=banner1 tells you the visitor came from Facebook, through a paid campaign called spring_sale, and clicked banner1 specifically.
This is the foundation of performance marketing: media buyers, affiliate teams and business owners make budget decisions based on data, not intuition. UTM tags work with Google Analytics, Amplitude, Keitaro, Binom, Voluum and virtually every other analytics or tracking platform.
The most common mistakes are inconsistent naming (facebook vs fb vs Facebook_Ads — analytics treats them as three different sources), spaces and non-Latin characters in values, and mixed case. This builder's live best-practice check catches all of them before the link ships, and the auto-clean option normalizes values to lowercase with underscores automatically.
UTM parameters do not affect SEO — they are analytics parameters, not page content. Just make sure your site uses canonical URLs so tagged links don't create duplicate pages in the index.
Everything runs locally in your browser with plain JavaScript — the URLs you build never leave your device.