Traffic Source Quality & UTM Hygiene Audit

Goal: audit source/medium quality and UTM hygiene for {START_DATE}–{END_DATE}. Data: GA4 BigQuery export `{PROJECT}.{DATASET}.events_*`, ad platform logs, server-side UTMs. Steps: 1) Classify sessions by source/medium/campaign; 2) Flag malformed or missing UTMs; 3) Compute quality metrics (bounce rate, engaged sessions, CVR, AOV, LTV proxy); 4) Rank sources by quality vs spend. Output: table of sources with UTM fix checklist and top 5 cleanup priorities.