When brands brief a retail media campaign, they usually start with their own buyers: people who've purchased the brand in the last 90 days. That's a reasonable starting point. But it's a ceiling, not a growth strategy.
Growth comes from reaching shoppers who don't currently buy your brand but are predisposed to. Category affinity is how you find them.
What category affinity means
Category affinity measures how strongly a shopper's behavior connects to a specific category, even if they haven't bought a particular brand within it.
A shopper who buys organic yogurt, granola, fresh berries, and almond milk has a strong affinity for health-oriented breakfast products. They haven't bought your brand's new protein cereal yet, but their basket composition says they're exactly the kind of person who would.
Affinity isn't what they declared in a survey. It's not an interest they clicked on a social platform. It's what they actually buy, repeatedly, with their own money. That's the strongest signal of future behavior that exists.
At Footprints AI, affinity is derived from the retailer's transaction data. We look at basket composition, purchase frequency within and across categories, brand switching patterns, and cross-category correlations. The result is a behavioral profile that predicts receptivity, not based on who the shopper is, but on what they do.
Why affinity beats direct targeting for growth
Direct targeting, reaching your existing buyers, is efficient for retention and frequency campaigns. But it has a natural limit: the pool of existing buyers is finite and often already loyal.
Affinity targeting expands the pool. It identifies shoppers who share behavioral patterns with your buyers but haven't crossed into your brand yet. These are the highest- probability new customers: they're already in adjacent behaviors, already buying from the category ecosystem your brand inhabits.
The conversion rates on affinity audiences are typically lower than direct buyer
audiences, that's expected, because you're reaching people who don't have an established habit with your brand. But the incrementality is higher, because every conversion is genuinely new.
This is where the real growth lives. Not in showing ads to people who already buy you.
In finding the ones who should be buying you and giving them a reason to start.
Affinity and shopping occasions
Affinity becomes even more powerful when layered with shopping occasion data.
A shopper with health category affinity who's on a Monday morning quick breakfast run is a very specific opportunity: they're predisposed to health products, they're in a breakfast context, and they're in a habitual purchase mode where a new brand can slot into their routine.
Compare that to: "women 25-44 who bought yogurt." Same general space, but the affinity + occasion combination is sharper. It tells you what the shopper is inclined to buy (affinity) and when they're most receptive (occasion). The targeting is tighter, the creative can be more specific, and the measurement can isolate the effect more precisely.
At the platform level, this means building audiences that combine behavioral affinity with temporal occasion patterns, and activating them across the right touchpoints:
offsite before the trip to build consideration, onsite during the trip to convert.
Building affinity models
Affinity models use transaction data to find behavioral similarity between shoppers. The most common approaches:
Co-purchase analysis. Shoppers who buy products A and B together frequently have
affinity for both categories. If your brand is in category A, shoppers who heavily buy category B but not A are affinity targets.
Basket composition clustering. Group shoppers by the overall shape of their basket, not individual purchases but patterns. Clusters of health-oriented, convenience-oriented, premium-oriented, family-oriented baskets emerge. Each cluster defines an affinity group.
Brand switching patterns. Shoppers who switch between brands within a category
are showing active category engagement. They're trying alternatives, which means they're open to your brand too.
Category trajectory. A shopper who recently entered a new category, started buying baby products, started buying organic, started buying premium wine, is in a transition phase. Their affinity is forming, and early brand presence can capture long-term loyalty.
These models run on the same data infrastructure that powers occasion identification and life stage segmentation. They're different lenses on the same behavioral dataset, the retailer's first-party transaction data.
Affinity for cross-category campaigns
One of the most underused applications of affinity is cross-category targeting.
A snack brand doesn't just compete with other snacks. It competes with every alternative a shopper might choose for a movie night, a party, a road trip, or an afternoon break. The competitive set is defined by the occasion, not the shelf.
Affinity data reveals these cross-category connections:
Shoppers who buy premium cheese also over-index on craft beer and artisan
crackers. That's a premium entertaining affinity.
Shoppers who buy sports drinks also over-index on protein bars and fresh fruit.
That's an active lifestyle affinity.
Shoppers who buy baby food also over-index on household cleaning products and organic produce. That's a new parent affinity.
Each of these connections creates a targeting opportunity that category-level targeting would miss. And each one can be activated through the retail media platform, reaching the affinity group across their relevant shopping occasions with creative that speaks to the shared context.
The bottom line
Category affinity is the fastest path to relevant targeting for growth campaigns. It identifies shoppers who are behaviorally predisposed to your brand, based on what they actually buy, not what they say they like.
When combined with shopping occasions and consumption moments, affinity creates the most precise audience definition available in retail media: shoppers who are inclined to buy (affinity), in the moment they're most receptive (occasion), with creative that matches the consumption context they're buying for.
Affinity is what they tend to buy. Occasion is when they tend to buy it. Together, they're the shortcut to performance.
Related Reading
- True Reach: What Reach Actually Means
- Sponsored Products: Retail Media at the Moment of Choice
- Occasion Frequency: How Often the Moment Happens Per Shopper
- Match Rate: The KPI That Limits Retail Media Proof
- Audience-Based Buying: The Future of Retail Media
Ready to see how this works in practice?
Footprints AI helps brands and retailers measure what matters. See our customer success stories or get in touch to discuss your retail media strategy.
