Ecommerce UTM builder.

A starting point for the developer

const KEYS=['utm_source','utm_medium','utm_campaign','utm_content','utm_term','gclid','fbclid','msclkid'];
const q=new URLSearchParams(location.search);
const hit={};KEYS.forEach(k=>{if(q.get(k))hit[k]=q.get(k);});
if(Object.keys(hit).length){
  hit.landing_page=location.href;hit.referrer=document.referrer;hit.at=new Date().toISOString();
  const save=(n,v)=>document.cookie=n+'='+encodeURIComponent(JSON.stringify(v))+';path=/;max-age=7776000;SameSite=Lax';
  if(!document.cookie.includes('utm_first='))save('utm_first',hit);
  save('utm_last',hit);
}

Request: store UTM data with every lead and order

Why: GA4 shows visits. Our database shows leads and sales. Saving the UTM tags with each record tells us which campaign produced each lead and how much revenue it brought in.

Steps:
1. Read the UTM tags and ad click IDs from the URL on every page load.
2. Save them in a first-party cookie for 90 days. Keep a first-touch copy that is never overwritten, and a last-touch copy that updates on each new tagged visit.
3. Ignore visits without UTM tags, so an untagged return visit never wipes the saved values.
4. Add hidden fields for every value to every form: contact, booking, sign-up and checkout.
5. Fill the hidden fields from the cookie when the form is sent.
6. Store each value in its own column on the lead or order record, and map the same fields into the CRM.
7. Test it: open a tagged link, send a form, and check the record shows the right values.

Fields to add:
- first_utm_source … first_utm_term: First tagged visit. Set once, never overwritten.
- last_utm_source … last_utm_term: Most recent tagged visit before the form was sent.
- gclid, fbclid, msclkid: Ad click IDs, for offline conversion uploads.
- landing_page: Full URL of the first page seen.
- referrer: The site the visitor came from.
- first_touch_at, last_touch_at: Timestamps of both visits.

Starting point:
const KEYS=['utm_source','utm_medium','utm_campaign','utm_content','utm_term','gclid','fbclid','msclkid'];
const q=new URLSearchParams(location.search);
const hit={};KEYS.forEach(k=>{if(q.get(k))hit[k]=q.get(k);});
if(Object.keys(hit).length){
  hit.landing_page=location.href;hit.referrer=document.referrer;hit.at=new Date().toISOString();
  const save=(n,v)=>document.cookie=n+'='+encodeURIComponent(JSON.stringify(v))+';path=/;max-age=7776000;SameSite=Lax';
  if(!document.cookie.includes('utm_first='))save('utm_first',hit);
  save('utm_last',hit);
}

Never put names, emails or phone numbers in UTM tags. Store them only in your own database, under your privacy policy.