How Debenhams quadrupled retail media revenue in 3 weeks with Mirakl Ads

By leveraging Mirakl Ads, the UK’s leading online department store achieved a 350% surge in daily ad spend and a massive boost in conversion rates, all while completing a full migration in just three weeks.

Intro

Debenhams is a storied UK department store brand that has undergone a successful digital transformation to become a leading online destination for Fashion, Beauty, and Home. It operates a fast-growing marketplace that hosts over 15,000 brands.

Driven by a "stock-lite" strategy, the marketplace has become a primary engine for growth, with third-party (3P) GMV now surpassing first-party sales on Debenhams.com. This massive seller base creates a significant opportunity for retail media, allowing Debenhams to offer targeted advertising solutions that drive visibility for brands and high-relevance experiences for shoppers.

Powering a digital leader

• Over 15K brands

• 3P > 1P: Third-party GMV exceeds first-party on Debenhams.com

• 6M+: Products available for advertisement

• Debenhams Group Ecosystem: Scalable infrastructure to reach additional high-traffic sites

The challenge: Evolving retail media to match Debenhams’ pace of growth

As Debenhams scaled its marketplace, the team’s retail media needs evolved quickly. Their existing set-up had supported early progress, but it became harder to keep pace with the volume of sellers, the speed of trading moments, and the rising expectations for relevance and performance. A few practical gaps started to emerge:

• Relevance at scale: As assortment expanded, Debenhams needed more consistent matching of ads to shopper intent to protect the customer experience and improve performance.

• Faster iteration: The team wanted a quicker cadence of optimisation and feature evolution to keep up with a fast-moving retail media landscape.

• Stronger performance upside: With ambitious growth targets, Debenhams needed more headroom to lift conversion and unlock incremental revenue from sponsored products.

• More hands-on enablement: They also looked for deeper support to help accelerate campaign optimisation, seller education, and day-to-day execution.

To stay ahead, Debenhams sought a retail media partner that could combine execution speed with stronger algorithmic capabilities — fit for a rapidly scaling seller ecosystem and an increasingly performance-driven environment.

Why Debenhams chose Mirakl Ads

Debenhams required a solution that could handle a massive campaign migration and a full platform replatforming — all during the high-stakes period leading up to the peak shopping season. Mirakl Ads was selected for its ability to deliver:

• Proven algorithmic quality: Mirakl Ads' AI-powered engine uses hybrid search (syntactic and vector) and multi-armed bandit (MAB) technology to ensure the most relevant products win every auction, significantly improving CTR and conversion.

• Marketplace integration: Designed specifically for marketplaces, Mirakl Ads offers a seamless self-service experience for 3P sellers, who can manage ads directly within their existing Mirakl back-office.

• Agility and speed: Mirakl’s ability to execute a complex migration — involving 1,300 campaigns and 6M products — in just three weeks was a decisive factor.

• Expert support: Debenhams valued the consulting-led approach and hands-on support provided by Mirakl to ensure the program's long-term success.

The results: A success story at scale in record time

Within just two months of switching from their previous provider to Mirakl Ads, Debenhams saw step-change improvements across every key performance metric.

• 4× revenue uplift: The “MVP” revenue baseline increased fourfold versus the previous solution.

• Stronger investment momentum: Advertiser investment increased significantly, with daily spend up ~350% over the period—reflecting growing seller confidence and the platform’s ability to scale efficiently.

• Significant conversion lift: Conversion rate (CVR) rose by +145%, demonstrating more relevant ad matching and better shopper experience.

• Broader advertiser participation: Active advertisers increased by +62% in the first few weeks, accelerating adoption quickly after launch.

Exceptional efficiency: ROAS more than doubled by +148%, showing that higher scale came with stronger performance — not trade-offs.

Future-proofing the Debenhams Group ecosystem

The success of Mirakl Ads on Debenhams.com has already paved the way for expansion. The program has already scaled to include boohoo.com, and future phases include the introduction of upper-funnel ad formats and the launch of retail media across additional websites within the Group.

By choosing Mirakl Ads, Debenhams has not only solved its immediate performance issues but has built a scalable, AI-driven retail media network that creates a "win-win-win" for the brand, its sellers, and its customers.

About Mirakl Ads

Mirakl Ads is the retail-first, AI-native retail media solution. As a self-service retail media platform, Mirakl Ads gives retailers complete control over ad inventory while enabling advertisers of all sizes to maximize performance. Powered by AI that prioritizes relevance and personalization, Mirakl Ads delivers smarter campaigns, higher fill rates and better returns for the entire ecosystem.

For more information: mirakl.com/products/mirakl-ads