The Google Display Network (GDN) is the collection of websites, mobile apps and Google-owned services, including YouTube and Gmail, where Google Ads can show display ads. Publishers join by selling their ad space through Google’s advertising products, and advertisers reach those spaces mainly through Display campaigns.
How the Display Network works
When a page or app on the network loads, its ad slot is put up for auction. Google looks at which advertisers want to reach that person or that kind of content, compares bids and ad quality, and shows the winner, all in a fraction of a second. The person might be reading a local news story, checking a recipe site, watching a YouTube video or playing a free game on their phone.
Advertisers decide where ads appear in two broad ways:
- By person: audiences such as previous site visitors, in-market groups, or customer lists. The ad follows the person across any site in the network.
- By place: named websites and apps (placement targeting), topics, or keywords describing page content. The ad appears in that context to whoever is there.
The network is separate from the Search Network, where text ads appear beside search results. They behave very differently: search reaches people who are actively looking, display reaches people who are doing something else.
Why it matters for a UK business
The size of the network is both its value and its risk. It lets a small brand appear on well-known UK publisher sites at a fraction of what a direct deal would cost. It also contains a long tail of thin content sites and apps where ads are seen by few people and clicked by accident.
A common and expensive surprise in inherited UK accounts is a search campaign with “Include Google Display Network” left ticked. Google offers this when a search campaign is created, and the result is that part of the search budget quietly goes on display placements, mixed into the same reports. Search performance then looks worse than it is, and nobody knows why.
Reporting needs care as well. Display clicks are cheaper and less deliberate than search clicks, and many display conversions are credited because an ad was seen rather than clicked. If those numbers are blended with search in a single report, decisions about where to put the next pound of budget are made on a misleading average. Segment by network, or keep display in its own campaigns, so each can be judged on its own terms.
Brand safety matters too. If you sell to families, operate in a regulated sector or simply care where your logo appears, you need to control the content your ads sit beside rather than leaving it entirely to the algorithm.
Common mistakes
- Running search campaigns with Display Network expansion switched on.
- Never checking where ads actually appeared.
- Leaving mobile apps fully open, when many accidental clicks come from games.
- Relying on default content settings when the brand needs stricter content suitability controls.
- Comparing display click-through rates with search and concluding display is broken.
How to act on it
- Open each search campaign’s settings and untick the Display Network option unless you have a deliberate reason to keep it.
- In Display campaigns, review the “Where ads showed” report and add placement exclusions to an account-level list so they apply everywhere.
- Set content suitability at account level: excluded content types, sensitive categories and inventory type.
- Measure display on conversions and assisted conversions, not on clicks.
Setting up these controls properly is part of the PPC management work I do, and it is one of the first things I check when I audit an inherited account.