An ad group is a container inside a Google Ads campaign that holds a set of closely related keywords and the ads written for them. The campaign decides budget, location and bidding; the ad group decides which searches you are matching and what message those searchers see.
How ad groups work
A campaign can contain many ad groups. In a search campaign, each ad group has its own keywords, its own ads (you can run up to three active responsive search ads per ad group), and optionally its own bids, assets and negative keywords. When someone searches, Google finds the keyword that best matches the search, and the ads from that keyword’s ad group are the ones that compete in the auction.
The principle is a single theme per ad group. If you are a London locksmith, “emergency locksmith”, “locked out of house” and “24 hour locksmith” belong together because one ad answers all three. “uPVC door lock replacement” is a different need with a different ad and a different landing page, so it belongs in its own ad group.
Other campaign types use the term differently. Display and video campaigns also have ad groups, built around audiences or placements rather than keywords. Performance Max replaces them with asset groups, which bundle creative and audience signals instead of keywords.
Why it matters
Ad groups are where relevance is won or lost. When the keywords in a group share one intent, you can write ads that echo the searcher’s words and send them to the right page. That lifts ad relevance and click-through rate, which feed into Quality Score and, in turn, into what you pay per click.
They also make reporting meaningful. If one ad group covers boiler repair and another covers boiler installation, you might find installations costing £40 per lead and repairs £12, and shift budget accordingly. Lump them together and you only see an average that describes neither.
Common mistakes
- One ad group per campaign with dozens of loosely related keywords, so the ad cannot speak to any of them specifically.
- The opposite extreme: hundreds of tiny ad groups, one per keyword, each with too little data to learn from. The old single keyword ad group method made more sense before match types loosened.
- The same keyword in several ad groups, so you cannot predict which ad will serve.
- Every ad group sending traffic to the homepage.
- Forgetting ad group level negative keywords to steer searches to the right group.
How to act on it
Group keywords by what the searcher wants, not by how the words look. A useful test: could one ad and one landing page answer every keyword in the group well? If not, split it. For most small UK accounts, five to fifteen keywords per ad group and a handful of ad groups per campaign is a sensible starting point, given that broad and phrase match already reach many variations.
Name ad groups so anyone can tell what is inside without opening them, for example “Emergency locksmith – Croydon” rather than “Ad group 3”. Clear names make reports readable, help when several people work on the account, and stop the same theme being built twice by accident.
Review the search terms report by ad group each month and move or exclude terms that land in the wrong place. Getting ad group structure right at the start is one of the first things I do when building Google search ad campaigns, because it is harder to fix once data has built up.