Channel cannibalization

How it works

A shopper searching for a product can meet the same store several times: its own Shopping ad, an ad for its listing on a marketplace, and an ad from its second store with the same catalogue. Each of these ads competes in Google’s auction. The shopper buys once, but the store can pay more than once: for a click on its own ad, then a marketplace commission if the shopper buys there.

Several of these ads can show on one results page, but not in the same ad location. Google’s Unfair advantage policy allows at most one ad for your business in a single ad location. It also asks related sites not to promote similar products and prices.

Each channel also sees only its own part of the shopper’s path: Google Ads sees the click on your ad, and the marketplace sees the sale. Before counting a channel as extra revenue, check how often its ads meet yours on the same searches. Our guide to your own channels in one auction shows how to run that check.

Where you see it

• Google Ads: the Auction insights report lists the domains of other advertisers in your auctions, with their overlap rate. If your second store’s domain is on that list, your own channels are meeting in the same auctions.
• Portal: the “Competitors in your niche” block on the feed screen shows two numbers for each site: how many times more often it appears than you, and in what share of shared queries it stands above you. Check whether a “competitor” there is your second store or a marketplace where you also sell.

Example

Example store, not client data.

The tableware shop’s Shopping campaign gets 400,000 impressions in a month. The owner also runs a second store, a kitchenware shop with the same supplier. It appears in Auction insights with an overlap rate of 35%: in 400,000 × 0.35 = 140,000 of those impressions, the owner’s two ads were on the page together.

Not to be confused with

• Campaign overlap — one product in several campaigns of one ad account. Only one of them enters each auction, so the cost is split data, not a second payment.
• Channel conflict — resellers and partners selling your products next to you, often cheaper. In channel cannibalization, every competing channel is yours.

Right and wrong readings

• Wrong: “A marketplace domain in Auction insights means our own listing outbid us.” Right: the report shows the domain, which covers every seller on that marketplace. It shows that the marketplace’s ads met yours, not whose product they showed.

Sources

• segments and metrics (Google Ads API) — participant domain and overlap rate in the Auction Insights report. Checked 2 October 2026.
• Unfair advantage (Google Advertising Policies Help) — one ad per business in a single ad location, related destinations. Checked 2 October 2026 (archived copy of 6 June 2026).