What This Rule Detects

Detects Yahoo Ads click ID (vmcid) without UTM parameters. GA4 does NOT recognize vmcid - traffic will be misattributed.

Why It Matters

Yahoo ads appear as "yahoo.com / referral" without UTMs. Cannot track campaign performance.

Required Setup:

✅ CORRECT: yoursite.com?vmcid=abc123&utm_source=yahoo&utm_medium=cpc&utm_campaign=search

How to Fix

In Yahoo Ads:

1. Add utm_source=yahoo
2. Add utm_medium=cpc or display
3. Add utm_campaign={{campaign}}
4. Keep vmcid enabled

FAQ

Does this create duplicate sessions?

No. Using both vmcid and UTMs is correct for GA4 tracking.

External Resources

• Yahoo Advertising Help