Headless Stripe Card Reader Entry at Zippin

Full Stack Software Engineer / Team Lead, Zippin, August 2019

Zippin builds checkout-free store technology. Overhead cameras and shelf sensors track what shoppers pick up, so they can leave without a traditional checkout. Entry still needed a way to identify the shopper and confirm they had a payment method on file.

At the time, the usual way into Zippin stores, and into other checkout-free retailers, was the app. Customers had to download it, create an account, and add a credit card before they could walk in. That is a lot of friction for a quick stop. App entry stayed available after we shipped card entry, but tapping a card was a much easier path and became by far how most people chose to enter.

In August 2019 I shipped card-reader entry for Zippin's San Francisco demo store using a Stripe Terminal Verifone P400 in headless mode. There was no iPad or cashier display. The reader stayed ready for a customer to tap or insert their card, without going through app onboarding.

The constraint

Stripe's Terminal JavaScript SDK was built around a staffed checkout flow, with a browser UI on an iPad or POS display where someone initiates the payment. That does not fit an unattended store entrance that needs to keep requesting a card on its own.

Stripe did not support running the Verifone P400 that way. The bundled front-end code assumed a browser-only environment.

Stripe Terminal Verifone P400 card reader at Zippin's SF demo store entry — Verifone P400 at Zippin's SF demo store.

The approach

I worked through Stripe's bundled JavaScript for Terminal and P400 control, and removed browser-only dependencies so the card reader command logic could run without a display UI. That let us run a headless service that kept the reader in a continuous collect-card state for store entry.

When a shopper tapped or inserted a card, we pre-authorized about $50 so we knew they could cover a reasonable amount of product, then opened the doors. Final charges still came from Zippin's normal post-shop reconciliation using the camera and sensor system.

Card entry demo at Zippin's SF demo store.

Risk I flagged to management

This depended on Stripe's bundled client code and backend behavior outside their documented, supported product path. I made that clear to management.

Stripe could update their backend or bundled front-end code and break how we used it.
I might be able to apply a similar fix to the new code, but only if the surface area still allowed it.

Management accepted that risk so we could ship the feature.

SF first, then Golden 1 Center

I implemented Verifone P400 entry for Zippin's SF store before any other checkout-free company had this kind of card reader entry, including Amazon.

In January 2020 we put a card reader in Zippin's new store at Sacramento's Golden 1 Center, home of the Sacramento Kings, where customers used it in a high-volume environment. Golden 1 Center announced it as the world's first in-arena checkout-free convenience store. Golden 1 Center partners with Zippin.

Zippin checkout-free store at Golden 1 Center in Sacramento — Zippin store at Golden 1 Center (Sacramento Kings), January 2020.

What I did

Adapted Stripe Terminal's bundled JavaScript so Verifone P400 control could run headless, without an iPad or cashier UI.
Added card entry alongside the existing app path. Shoppers could tap or insert a card, get a ~$50 pre-auth, and enter the store. That was a much lower barrier than app onboarding and became by far the preferred way in.
Shipped the feature for Zippin's San Francisco demo store (August 2019) before competitors, including Amazon.
Flagged the Stripe upgrade-breakage risk to management before we shipped.
Deployed the same card-reader entry model to Golden 1 Center in Sacramento (January 2020).