What Is an Ad Group?
Google Ads organises paid search accounts in a three-tier hierarchy: account, campaign, and ad group. The account is the top level. Campaigns sit inside the account and control budget, bidding strategy, geographic targeting, and network settings. Ad groups sit inside campaigns and group a specific set of keywords together with the ads that serve for those keywords. Every keyword in a Google Ads account must belong to an ad group, and every ad must belong to an ad group.
Ad groups exist to ensure that when a search query matches one of your keywords, the most relevant ad possible is shown. If all your keywords were in one group with one set of ads, a plumbing business's ad about "toilet repairs" would also appear for searches about "bathroom renovations" and "geyser installations", even though those are different services with different messaging needs. By splitting keywords into separate ad groups, each with its own tailored ad copy, you ensure that the right message reaches the right searcher, improving relevance, click-through rate, and ultimately Quality Score.
Quality Score is a Google metric from 1 to 10 that factors in expected click-through rate, ad relevance, and landing page experience. A tightly themed ad group where keywords, ads, and landing page all share the same specific intent will typically achieve a higher Quality Score than a loosely organised group. Higher Quality Scores reduce the cost per click you need to pay to achieve a given ad position, meaning well-structured ad groups directly affect campaign efficiency and cost.
Ad Group Structure for SA Businesses
South African businesses advertising on Google often make the mistake of putting every keyword into a single ad group or creating a handful of ad groups based on broad service categories. A Johannesburg-based plumbing company might have one ad group called "Plumbing" containing keywords like "plumber Johannesburg", "blocked drain Johannesburg", "geyser repair Sandton", "burst pipe Randburg", and "bathroom installation Midrand". A single set of ads cannot speak relevantly to all of these search intents, and the Quality Scores will suffer as a result.
Better practice is to create separate ad groups for each distinct service and intent cluster:
- Emergency Plumbing: keywords like "emergency plumber Johannesburg", "24hr plumber near me", "burst pipe repair urgent"
- Blocked Drains: keywords like "blocked drain Johannesburg", "blocked toilet plumber", "drain cleaning service Johannesburg"
- Geyser Services: keywords like "geyser repair Sandton", "solar geyser installation Johannesburg", "geyser replacement cost"
- Bathroom Renovations: keywords like "bathroom renovation Johannesburg", "bathroom installer Midrand", "bathroom remodel quote"
Each ad group then has ads and a landing page URL that speak directly to that specific service. A user searching "emergency plumber Johannesburg" sees an ad about emergency callouts with a phone number front and centre. A user searching "bathroom renovation Johannesburg" sees an ad about renovation services with before-and-after imagery in the extension. The relevance improvement translates directly into better performance and lower cost per click.
Ad Groups and Bidding Strategy
Bid settings can be applied at campaign or ad group level, depending on your bidding strategy. With manual CPC or Enhanced CPC bidding, you can set a default CPC bid at the ad group level, which all keywords in that group inherit unless overridden at keyword level. This is useful for setting different default bids for high-value versus lower-value ad groups within the same campaign. For example, a legal practice might set a default bid of R80 per click in an ad group targeting "personal injury lawyer Cape Town" and R25 per click in an ad group targeting informational queries like "what is a personal injury claim".
With Smart Bidding strategies such as Target CPA, Target ROAS, or Maximise Conversions, the bidding is controlled at campaign level and the algorithm sets bids for individual auctions automatically. Ad group structure is still important under Smart Bidding, but for a different reason: conversion data is pooled at the campaign level, so tightly themed ad groups with good keyword coverage help the algorithm learn which search intents convert for your business, improving its bidding decisions over time.
Well-structured ad groups also make it easier to identify performance problems. If a campaign is underperforming, reviewing at the ad group level shows which service or keyword theme is responsible. A Cape Town estate agency might find that their "property to rent Cape Town" ad group has a strong conversion rate while their "property for sale Cape Town" ad group is generating clicks but no enquiries. Without clear ad group separation, this signal would be invisible in the combined campaign data. With separate ad groups, it is immediately actionable: either the sales landing page needs work, or the search intent of buyers requires different ad messaging.
FAQ
How many keywords should an ad group have?
Best practice is to keep ad groups tightly themed, typically 5 to 20 closely related keywords. SKAGs (single-keyword ad groups) were popular for maximum control but are now less necessary because responsive search ads and Smart Bidding handle variation well. In South Africa, where search volumes are lower than in larger markets, a balance of 5 to 15 tightly themed keywords per ad group works well for most service businesses.
What is the difference between an ad group and a campaign?
A campaign is the top-level structure that controls budget, bidding strategy, network settings, and geographic targeting. An ad group sits inside a campaign and groups a specific set of related keywords with the ads that serve for them. One campaign can contain many ad groups. You might have a campaign for 'Plumber Johannesburg' with ad groups inside it for 'emergency plumber', 'blocked drains', and 'geyser installation', each with its own relevant ads and landing pages.