GA4 funnel analyst

Funnel reports tell you that people leave. This skill tells you where it is worst, for whom, and what to change first.

When to use

• Weekly, on a GA4 export of the ecommerce events (view_item, add_to_cart, begin_checkout, add_shipping_info, add_payment_info, purchase).
• After a checkout release, comparing the week before and after.

Input

Event counts per step, broken down by device category and session source/medium, for the period and a comparison period. Optional: page load times per step.

Process

1. Sanity check the data. Each step must be ≤ the previous one. If purchase > add_payment_info, the tagging is broken — report that and stop; a funnel on bad events is worse than no funnel.
2. Compute step conversion for the whole period, then per device, then per source. Report absolute counts next to percentages.
3. Find the worst leak: the step whose conversion is lowest relative to the site's own baseline (the comparison period), not relative to industry numbers.
4. Find who leaks most at that step. A segment counts only with ≥ 200 sessions entering the step; smaller segments are listed as "too small to judge".
5. Pick one fix. The smallest change that addresses the worst leak for the biggest segment. One, not a list.

Rules

• Percentages without counts are forbidden. "Mobile checkout converts 12% worse" must carry "(1 840 → 1 620 sessions)".
• Never compare against benchmarks from memory. The only baseline is the site's own comparison period.
• Correlation is a hypothesis: "mobile drops at shipping" is a place to look, not a diagnosis. Say what would confirm it (a session recording, a form-error log).
• Do not recommend more than one change. If the second-worst leak is close, mention it as next week's candidate.

Output format

## Funnel — 1–7 Sep vs 25–31 Aug
| step | sessions | conv. | Δ vs prev |
| add_to_cart → begin_checkout | 12 400 → 4 960 | 40.0% | −3.1 pt |
| begin_checkout → add_shipping_info | 4 960 → 3 210 | 64.7% | −9.8 pt |  ← worst leak
...

## Where it leaks
Mobile · organic: 58.1% (1 320 → 767) vs desktop 74.2%. Paid social mobile too small to judge (140).

## Try first
Shipping step on mobile: the address form. Confirm with form-error events on `address_line_1`; if errors > 15% of attempts, enable autocomplete and ship.

License

MIT