Onsite describes advertising sold on a retailer's own digital properties: the website, the mobile app, and the search, category, and product pages a shopper passes through on the way to a basket. IAB Europe's harmonized definition, published on March 26, 2025 and repeated in the association's July 2025 101 Guide to Retail and Commerce Media, puts it plainly: on-site advertising is sold on a commerce platform or a retailer's owned and operated websites and apps, and typically takes the form of Sponsored Products, Sponsored Display, and display and video. The term exists because retail media split into three environments that behave differently. Onsite runs where the retailer controls the page. Offsite uses retailer data to buy inventory somewhere else. In-store runs on screens and audio inside the physical shop.

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The distinction is not cosmetic. Onsite is the only one of the three where exposure and transaction happen inside the same company's systems, which is why it produces the tightest sales reporting in digital advertising and the weakest independent verification.

Where onsite sits in the transaction

A shopper types a query into a retailer's search box. Before results render, the retailer's ad server runs an auction against the slots reserved for sponsored placements in that result set. Advertisers, usually brands that sell through the retailer, bid on keywords, product categories, or specific competitor items. Bids are ranked against relevance and conversion signals drawn from the retailer's own catalogue and purchase history, so the highest bid does not automatically win. Sponsored product slots are almost always priced on a cost-per-click basis. Banner, homepage takeover, and video placements are typically sold on a cost-per-thousand-impressions basis or as fixed-price sponsorships.

Two features separate this from ordinary display advertising. First, the creative does not come from the buyer. The retailer assembles the ad from its own product feed, pulling the image, title, price, rating, and availability that already exist in its catalogue, which is why sponsored listings look identical to organic results apart from a "sponsored" label. Second, the auction is closed. Historically the retailer operated the ad server, the demand interface, and the measurement system, with no third party sitting between the bid and the impression.

The buy side is fragmented by design. Brands run campaigns through retailer self-service consoles, through managed service teams at the retailer, or through bid-management platforms such as Pacvue and Skai that connect to dozens of networks by API. On the sell side, a small number of technology suppliers do the actual serving: Criteo, Epsilon, Koddi, Topsort, Kevel, Pentaleap, Mirakl, and Amazon's own Retail Ad Service among them. Very few retailers outside Amazon and Walmart have built the stack themselves.

The product feed problem

Programmatic buying arrived late to onsite for a technical reason. Standard real-time bidding assumes the buyer supplies a finished creative. Product listing ads do not work that way, and retail search pages cannot tolerate the latency budget of a conventional exchange call.

IAB Tech Lab addressed the first half of that problem with an extension to the OpenRTB protocol, released for public comment in December 2024 and finalized on January 24, 2025. The extension introduces a prodfeed object inside the bid request, at bidrequest.ext.prodfeed, whose presence signals that a bidder must understand a product feed to transact on the impression. The object carries information about the feed and about allowed and blocked products and categories. The Native Ads API 1.2 gained a matching data type, number 13, for Product ID, so a buyer can respond with nothing more than an identifier and leave the store owner to compile the ad from brand name, description, rating, and price. The specification deliberately stops short of defining the structure of a product feed itself.

The latency half was tackled commercially. Pentaleap and Teads announced on July 24, 2025 what they described as the first real-time bidding integration for onsite sponsored product ads across multiple retail networks, built around ad serving fast enough for a retail search page. Andreas Reiffen, chief executive and co-founder of Pentaleap, said in the announcement that retailers could run sponsored product ads through real-time bidding for the first time.

From Amazon's search results to a defined category

The format predates the vocabulary. Amazon began selling sponsored placements inside its own search results in 2012, and by August 2023, when the company started extending Sponsored Products to third-party sites including Pinterest and BuzzFeed, trade coverage was describing it as a decade-old product. Walmart, Target, Kroger, and the European grocers followed, each starting with sponsored listings before adding display, then offsite, then in-store.

Standardization lagged the money by roughly a decade. IAB and the Media Rating Council released the Retail Media Measurement Guidelines in January 2024, after a September 2023 draft, with an explicit scope covering ads that appear onsite, offsite, online, and in-store. IAB Europe published its own measurement standards in April 2024, in-store definitions with IAB in September 2024, and the pan-European three-way definition in March 2025. Certification followed: Albert Heijn became the first network certified under IAB Europe's program on September 24, 2025, with a scope covering static display and sponsored products across its onsite website and app.

Spelling still splits by geography. IAB and IAB Tech Lab in the United States write "onsite" as one word. IAB Europe writes "on-site" with a hyphen. Both refer to the same inventory.

Why the category matters

Onsite carries most of the money. IAB Europe reported that European on-site retail media spend grew 22.2% in 2024 to exceed 10 billion euros, against a total European retail media figure the association put at 13.7 billion euros with 21.1% growth in its October 2025 statistics release. Those two IAB Europe figures do not sit easily with the 11.1 billion euro market and 22.1% growth cited in its March 2025 definitions material, and the association has not reconciled the two publicly. Amazon, whose advertising business is built primarily on sponsored listings, reported full-year 2025 advertising revenue of 68.6 billion dollars and passed 70 billion dollars on a trailing twelve-month basis by early 2026.

Inventory is also still expanding. Pentaleap's H2 2025 benchmarks, drawn from 2,500 keywords across 12 United States networks including Amazon, Walmart, Target, and Kroger, found sponsored product coverage up 7% year over year, with retailers replacing fixed ad slots with algorithmically placed ones. Albertsons increased coverage 81% to reach 73% of measured search results.

Where onsite fails

Verification is the structural weakness. The IAB/MRC guidelines state that retailer site restrictions generally make onsite viewability tagging impossible for each advertising partner, while still recommending that retailers supply viewability metrics. The same document requires retailers to disclose in advance which properties and affiliate domains count as onsite rather than offsite, an instruction that would be unnecessary if the boundary were obvious.

Attribution is contested for a different reason. Each network measures conversions inside its own walls, so a shopper exposed at one retailer and converting at another is invisible; analysis of that gap published in June 2026 argued siloed measurement understates upper-funnel contribution. Buyers have pressed for incrementality rather than reported return on ad spend, and the Australian retailer Metcash went further in 2026, warning that networks risk recycling trade dollars rather than winning new budget. Agency satisfaction with retail media networks fell from 66% to 44% between surveys presented at IAB Australia's 2025 summit even as budgets rose about 20%. IAB Europe's July 2025 guide recorded 53% of buyers naming absent standards as a barrier to investment. Ad load is the quieter complaint: every additional sponsored slot displaces an organic result the merchandising team selected.

Disambiguation

Offsite uses retailer first-party data to buy inventory the retailer does not own, across display, video, social, connected TV, digital out-of-home, and audio. The data is the retailer's; the screen belongs to someone else. In-store covers screens, audio, and connected shopping formats inside the physical shop, governed by a separate IAB and IAB Europe standard. Onsite optimization in search engine optimization means on-page work such as titles, internal linking, and markup, and has no connection to retail media. Trade marketing covers retailer-planned activity such as circular features, promotions, and loyalty offers, funded by the brand but not sold as media.

One edge case resists all four labels. When Amazon extended Sponsored Products to publisher sites in 2023, the format stayed the same while the environment changed, producing an ad that is onsite by mechanics and offsite by placement.

Recent developments

Access has been the theme since late 2025. Criteo became Google's first onsite retail media partner for Search Ads 360 on September 10, 2025, opening a network of more than 200 retailers to buyers working inside Google's interface. The Trade Desk followed on October 9, 2025, connecting to Koddi's commerce media platform with Gopuff as launch partner. Amazon's Retail Ad Service, announced at CES on January 9, 2025, let other retailers run sponsored products on Amazon's technology; Macy's Media Network integrated it in late 2025.

The pattern continued through 2026. Koddi placed its commerce media network inside Search Ads 360 in June 2026, as noted in coverage of its GIPHY partnership. Delivery platforms joined: Wolt opened in-app inventory to programmatic buyers in Germany in May 2026, and Deliveroo Media launched programmatic advertising on its order tracker page across four markets on July 27, 2026, with a 20% rate-card discount. Research cited in February 2026 coverage of THG's data partnership found more than 95% of media buyers open to purchasing onsite retail media programmatically. The closed auction that defined onsite for a decade is being opened, slot by slot.

Timeline

  • 2012: Amazon begins selling sponsored product placements inside its own search results
  • August 2023: Amazon extends Sponsored Products to third-party publisher sites
  • September 13, 2023: IAB and MRC release draft Retail Media Measurement Guidelines for public comment
  • January 2024: IAB and MRC publish the final Retail Media Measurement Guidelines
  • January 18, 2024: IAB Europe publishes its first pan-European retail media capability map
  • April 25, 2024: IAB Europe releases final European Retail Media Measurement Standards
  • September 18, 2024: IAB and IAB Europe release first in-store retail media definitions and standards for public comment
  • October 2024: IAB Europe launches its retail media certification program
  • December 2024: IAB Tech Lab opens the OpenRTB product listing ad extension for public comment
  • January 9, 2025: Amazon announces Retail Ad Service at CES
  • January 24, 2025: IAB Tech Lab finalizes the OpenRTB product listing ad extension
  • March 26, 2025: IAB Europe publishes updated pan-European on-site, off-site, and in-store definitions
  • July 24, 2025: Pentaleap and Teads announce real-time bidding for onsite sponsored product ads
  • September 10, 2025: Criteo becomes Google's first onsite retail media partner for Search Ads 360
  • September 24, 2025: Albert Heijn becomes the first IAB Europe certified retail media network
  • October 9, 2025: The Trade Desk enables onsite retail media buying through Koddi
  • December 2025: Pentaleap reports sponsored product coverage up 7% across 12 United States networks
  • May 2026: Wolt opens in-app retail inventory to programmatic buyers in Germany
  • June 2026: Koddi connects its commerce media network to Google Search Ads 360
  • July 27, 2026: Deliveroo Media launches programmatic order tracker inventory in four markets

Summary

Who: Retailers and marketplaces operating the inventory, endemic brands and their agencies buying it, and a supplier layer including Criteo, Koddi, Epsilon, Topsort, Pentaleap, and Amazon Retail Ad Service that builds and serves it. Standards come from IAB, IAB Europe, IAB Tech Lab, and the Media Rating Council.

What: Advertising sold on a retailer's owned and operated website and app, covering sponsored product listings, sponsored display, banners, video, takeovers, and checkout placements, with creative assembled by the retailer from its own product feed.

When: Established commercially from 2012 through Amazon's sponsored search placements, defined formally by IAB and MRC in January 2024 and by IAB Europe in March 2025, and opened to programmatic buying from the OpenRTB product listing ad extension of January 24, 2025 onward.

Where: Inside retailer search results, category pages, product detail pages, homepages, and checkout flows, on desktop, mobile web, and retailer apps.

Why: Onsite reaches shoppers at the point of decision and links exposure to a recorded transaction inside one company's systems, which produces the strongest sales reporting in digital advertising and, for the same reason, the weakest independent verification.