What is funnel drop-off?
Funnel drop-off is the share of sessions lost between consecutive steps of a purchase: page view, product view, add to cart, checkout, purchase. It is a session count at each step, not an event count, so a visitor who adds three products still counts once at the cart step.
Formula
step conversion = sessions reaching step k ÷ sessions reaching step k−1
overall conversion = purchase sessions ÷ all sessions
Steps are cumulative: a session that purchased is counted at every earlier step whether or not the pixel saw those clicks. Without that rule the rates could exceed 100%, because the storefront pixel only reports a product view on pages that expose a product id, and the checkout step fires again on the confirmation page.
Worked example
Over 30 days: 4,000 sessions, 2,400 product views, 900 carts, 420 checkouts, 310 purchases. Cart → checkout is 47%; checkout → purchase is 74%. The biggest loss is between product view and cart (62% drop), which points at pricing or product-page friction rather than the payment step.
How Saldo Metrics computes it
v_pixel_session folds raw pixel events into one row per session with
first-event UTM, device and country and a traffic_channel bucket (paid,
email, campaign, organic search, referral, direct — a heuristic from the UTM
medium and the referrer, not an attribution model). v_funnel_dropoff
aggregates those sessions per day and dimension. Any day at least two days
old that has a roll-up row is served from fact_funnel_daily instead of the
raw events; the roll-up exists so this history survives once the org's pixel
retention window later scrubs the underlying identifiers.