Shopify theme · A/B framework

Nine Below

A conversion-optimised Shopify theme for a spirits brand, with experiment assignment, a fail-closed age gate and off-domain checkout instrumentation built into the theme rather than bolted on as an app.

Nine Below is a fictional brand. It exists to exercise the theme against a real-looking identity. No product, company or endorsement here is real, the press quotes are invented and labelled as such, and every image is generated and unbranded.

View the site Paid-social flow

You will meet the age gate first — that is the point of it.

What is actually interesting here

The age gate cannot fail open. A blocking stylesheet above <body> establishes the closed state; JavaScript's only job is to open it. JS disabled, a thrown script, or a 404 on any asset all leave the gate up and the content hidden.
Variants are assigned before first paint. Inline and blocking, so nobody sees arm A flash before arm B — which would otherwise bias the very result you are measuring.
Exposure is counted when the visitor can actually see the thing. Impressions are held behind the gate, because counting someone who never got past it deflates every conversion rate and makes the sample-size target too small.
Checkout is off-domain, so the funnel is instrumented from the outside and the experiment arm is carried into the retailer's UTM payload — the only way the result reconciles to revenue.
An offer test, not just a copy test. One experiment swaps the entire proposition — a $69.99 bottle for a $199.99 bundle — and removes the cheaper CTA rather than adding a second one. It is scoped to a single platform, and it is read on revenue per visitor: at three times the price an arm can convert far worse and still be worth more, and a conversion-rate verdict would kill the better offer.
The offer section is hidden by a positive match, not a negation. It appears only for a visitor explicitly assigned to that arm, so an unregistered, parked, held-out or entirely broken experiment leaves it hidden. The opposite polarity would leak a $199.99 offer to everyone the moment anything upstream failed.
The landing adapts to the platform that sent you. Instagram, TikTok and Facebook get their own headline and their own degree of stripping, resolved before paint from the campaign parameters, the referrer, or the in-app browser itself. Every event carries the channel, so TikTok's much higher age-gate rejection rate never hides inside a blended number.

Try the framework

URL	What it does
?ab=age_gate:b	Forces the birthdate age gate instead of the one-tap version
?ab=hero_image:b	Forces the alternate hero image
?ch=ig&ab=bundle_offer:b	The $199.99 bundle offer, which replaces the single-bottle CTA. Needs `ch=ig` — the experiment only enrols Instagram traffic
?ch=ig&ab=bundle_offer:a	The control for that test — the single bottle at $69.99
?ab=reset	Clears assignments and re-buckets you
?agegate=reset	Re-opens the age gate after you have confirmed
?debug=1	Shows the live GA4 event inspector
?flow=focus	The stripped-back view served to paid-social traffic
?ch=ig	The Instagram landing — visual-led headline
?ch=tt	The TikTok landing — hook headline, tighter fold
?ch=fb	The Facebook landing — nav kept on desktop

This demo does send analytics. It is wired to a real GA4 property so the funnel can be verified end to end, and page views, age-gate outcomes, experiment exposures and cart events are recorded. Nothing identifies you, and no personal data is collected or requested. If you would rather not be counted, do not proceed past the age gate — nothing is sent until you do.

The cart is a mock. No order can be placed, no payment details are ever requested, and nothing reaches a retailer. Add ?debug=1 to any URL to watch the exact event stream this page produces.

Repository

Standard Shopify theme layout — layout/, sections/, snippets/, config/, assets/. Every experiment, colour and font is a theme setting, so re-skinning means editing settings rather than code. preview/ is a static mirror of the rendered theme so it can be served without a Shopify store.

See the README for the full reference.