Proving Prime Video ads drive subscriptions for Butternut Box

The challenge

Butternut Box sells premium fresh dog food on subscription in a UK market still dominated by a handful of category incumbents. London is the brand's most important market and its most expensive: the pet parent audience is saturated, media consumption is fragmented and the cost of reaching a new customer keeps rising.

The brand was already investing heavily in linear TV and out-of-home. The question was whether streaming video could add incremental reach on top of that without diminishing returns, and whether it could be shown to do more than build awareness. Fresh-frozen subscription is a high-loyalty, high-switching-cost category. Converting a broad awareness message into a measurable new subscription is the hard part.

The brief: extend the London media mix into Prime Video, and prove, not assume, that it drives customers to the site and through checkout.

The approach

We integrated Prime Video ads as a London-specific extension of the existing broadcast and out-of-home plan, then closed the attribution gap that broadcast had always left open.

The first step was a custom deployment of the Amazon Ad Tag on the Butternut Box storefront, capturing post-exposure behaviour on-site: page views, add-to-cart events and subscription sign-ups. That gave us a first-party signal that could be joined to ad exposure.

The join happened in Amazon Marketing Cloud. Using AMC as the clean room, we matched Prime Video exposure against the on-site events to measure incremental reach and frequency, and to trace the path from a streaming impression to a site visit and a subscription. Post-view behaviour that would otherwise have been invisible became a measurable outcome.

That measurement fed straight back into the plan. AMC told us the frequency at which acquisition efficiency peaked and where additional reach stopped adding value, so budget was allocated on evidence rather than on planning assumptions.

The result

Prime Video delivered new customers at a cost per acquisition well under a third of the target set at the outset, and reached more Londoners than planned while holding frequency below the ceiling we had set. Against comparable streaming and broadcaster video-on-demand channels in the same mix, it produced higher incremental reach for the budget.

Because the Amazon Ad Tag was in place, the funnel was visible end to end. AMC attributed measurable add-to-cart and conversion rates to post-view traffic, positioning streaming video as a conversion channel rather than an awareness line on the plan. A first-party brand lift study confirmed an uplift in awareness alongside it.

The commercial signal followed. Butternut Box more than tripled its Amazon Ads investment for the following year and extended the streaming plan into Netflix inventory.