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Commerce media: how to tell if you have an opportunity
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Retail media has transformed marketing by giving greater visibility into the entire customer journey. For most customers, buying is a journey involving multiple touchpoints across different channels, from brand app, review sites, to in-store try-ons. This is exactly where retail media is empowering marketers.
Using retailer's first-party data insight, retail media gives marketers visibility and measurement of customer touchpoints as they browse and shop, from first click to post-purchase. And in an era where GDPR and growing privacy regulations have made third-party data increasingly restricted, reliance on retailer first-party data means measurement has also become privacy-compliant by design.
Let's dive into how retail media networks are revolutionising ad measurement and allow marketers to measure what actually drives sales.
Retail media measurement links the ads a brand runs with a retailer, onsite, offsite or in store, to what shoppers then buy. Because the retailer holds the transaction data, it can connect ad exposure to completed sales, online and in store, rather than relying on clicks and impressions alone.
At the core of successful ad measurement is first-party data collected from shopper interactions within a retailer's ecosystem. This first-party data is highly accurate and provides insights into customer behaviour (searches, purchase history, wish lists, engagement with digital ads) unavailable anywhere else.
With this data, brands can focus on improved KPIs like purchase intent and conversion rates across channels. This bird’s eye view of ad performance is critical as brands seek to optimise their ad spend for both immediate impact and long-term success.
Conventionally, marketers have relied on metrics like clicks, conversions and Return on Ad Spend (ROAS) to gauge campaign success. However, to truly drive growth in the long run, they must focus on making every customer interaction unique and personal. For this, marketers need to understand what led to the sale, as well as the sale itself.
Retail media follows the customer journey from first ad interaction to post-purchase behaviour. A marketer can now see which touchpoints influenced the purchase decision and optimise campaigns for those touchpoints.
For example, by leveraging the Epsilon Retail Media platform, marketers can track detailed views of customer interactions with digital ads or content, including clicks, video views, dwell times, and add-to-cart actions. Marketers can determine if a customer is actively considering a purchase or is just browsing by analysing these activities and then personalise communications accordingly.
Measurement also needs to reach the shop floor, because many purchases still happen in store. Epsilon's in-store sales attribution links onsite retail media to in-store purchases, giving closed-loop measurement across online and offline sales.
Reaching a customer before they buy typically requires multiple touchpoints, and the exact number will vary depending on competition, category and the customer's stage in the journey. Marketers need to track, personalise and measure the impact of each of these interactions to drive a sustainable growth strategy. Some of the key actionable steps include:
Use multi-touch attribution to understand the full customer journey
Not all touchpoints contribute equally to a purchase, and treating them as if they do leads to misallocated budget. Multi-touch attribution tools assign value across each interaction in the customer journey, from the first awareness-stage ad through to the final conversion, giving marketers a clearer sense of which channels and formats are genuinely influencing decisions. This is especially important in retail media, where a shopper might engage with an onsite sponsored product ad, see an offsite display ad later in the week, and then convert in-store. Without attribution that spans those touchpoints, the picture is incomplete.
Optimise campaigns in real time based on what the data is telling you
One of the practical advantages of retail media is access to live performance data that allows campaigns to be adjusted while they are still running, rather than waiting until they have ended. If a particular ad format, audience segment or creative variant is outperforming others mid-flight, budget can be reallocated accordingly. For example, if ads featuring customer reviews are generating stronger engagement than product feature creatives, that signal can be acted on immediately, whether by shifting spend, testing new messaging or introducing a time-limited offer to capitalise on the momentum.
Balance short-term ROAS with longer-term growth metrics
While ROAS can be a useful short-term indicator, it only tells part of the story. A campaign that drives a high ROAS on a single transaction may still be underperforming if it is not contributing to repeat purchases or longer-term loyalty. Marketers should track metrics like customer lifetime value (CLV), retention rates and incremental sales alongside ROAS to build a more complete picture of campaign effectiveness. In retail media particularly, where the same customer may interact with a brand across multiple visits before converting, this longer view is essential for making confident investment decisions. The most reliable way to show incremental sales is a test-and-control comparison: shoppers who saw the ads against similar shoppers who did not.
Build post-purchase into your measurement strategy
Measurement should not stop at the point of conversion. Post-purchase behaviour, including repeat buying patterns, basket size changes and response to loyalty communications, provides some of the most valuable signals for understanding whether a campaign has genuinely built customer value or simply driven a one-off transaction. Incorporating post-purchase data into campaign reporting allows marketers to identify which audiences are most likely to become long-term customers and to tailor future campaigns accordingly.
No single number shows whether retail media is working. Use a mix that covers short-term efficiency, what the ads actually caused and whether the customers they win come back.
| KPI | What it tells you | Use it to |
|---|---|---|
| ROAS | Revenue for every pound of ad spend | Judge short-term efficiency |
| Incremental ROAS (iROAS) | Revenue the ads caused, measured against a control group | Prove value and set budgets |
| New-to-brand customers | Share of buyers who had not bought the brand recently | Track acquisition |
| Repeat purchase rate | Whether new buyers come back | See longer-term value |
| In-store sales lift | Change in store sales among shoppers who saw the ads | Capture the full omnichannel effect |
| Click-through and add-to-basket rates | Early engagement with the ads | Optimise while the campaign runs |
Start by agreeing what success means with your retail media partner before the campaign runs: which sales count, over what window, and against which control group. Epsilon Retail Media measures onsite, offsite and in-store outcomes for each campaign, with CORE Identity matching ads to real shoppers rather than devices.
1. What is the difference between ROAS and incremental ROAS in retail media?
ROAS measures the revenue generated for every pound spent on advertising, but it can be misleading in retail media because it often captures sales that would have happened anyway, with or without the ad. Incremental ROAS (iROAS) isolates the uplift that is directly attributable to the campaign, separating genuine ad-driven conversions from organic purchases. For retail media specifically, where shoppers are often already in-market, iROAS gives a more accurate picture of whether your spend is actually changing behaviour or simply claiming credit for it.
For a fuller comparison, see ROAS vs incremental ROAS.
2. How does retail media measurement differ from traditional digital advertising measurement?
Traditional digital advertising typically measures performance through proxy metrics such as clicks, impressions and click-through rates, which do not confirm whether a purchase actually occurred. Retail media measurement can go further because the retailer owns the transaction data. This means it is possible to link ad exposure directly to a completed sale, both online and in-store, and attribute that outcome to a specific shopper rather than an anonymous device. This is closed-loop reporting that connects media spend to real business outcomes rather than assumed ones.
3. What role does identity resolution play in retail media measurement?
Accurate measurement depends on being able to recognise the same person across multiple touchpoints and devices throughout their shopping journey. Without reliable identity resolution, a brand cannot tell whether the customer who saw an ad on their phone is the same person who later bought in-store. Epsilon's CORE Identity uses deterministic name and address matching to build a stable, durable view of individual shoppers, which means impressions can be tied back to transactions with confidence, even where the path to purchase spans several days, channels or devices.
