The essentials
- Definition: a custom segment is an audience you describe yourself from keywords searched on Google, URLs visited or apps used, instead of choosing a predefined category.
- Where it applies: Display, Video, Demand Gen and Performance Max (as a signal); not in Search campaigns, where it only serves for observation.
- The most reliable signal: search keywords, which reflect a real intent; competitor URLs act as a complement.
- Useful size: between 50,000 and 500,000 users in France for a campaign that delivers without being drowned out.
Google’s predefined audiences (affinity, in-market, demographics) are broad and shared with every advertiser. Custom segments, formerly “custom audiences”, let you describe an audience from what it searches for, visits or installs. Built properly, they target an intent rather than a profile. This article explains how to create them, which campaigns they really count in and what makes them ineffective.
What a custom segment is
Since the merger of “custom affinity audiences” and “custom intent audiences” in 2020, Google Ads offers a single type of custom segment, defined by three families of signals:
| Signal | What Google does with it | Trustworthiness |
|---|---|---|
| Keywords (search terms) | Targets people who have searched for these terms on Google, or who have an interest in these topics depending on the campaign | High: reflects an intent |
| Site URLs | Targets people who browse sites similar to those given, not necessarily those exact sites | Medium: approximation by similarity |
| Apps | Targets users of apps similar to those given | Medium, mainly useful for app campaigns |
The point often misunderstood: entering a competitor’s URL does not target its visitors. Google uses the URL to understand the type of content and looks for users whose browsing behaviour resembles it. The actual targeting stays probabilistic.
Creating the segment in practice
- Open Tools, then Audience manager, then Custom segments.
- Choose between “people with any of these interests or purchase intentions” (broad interpretation) and “people who searched for any of these terms on Google” (strict interpretation, reserved for YouTube, Discovery and Demand Gen campaigns).
- Enter 10 to 30 consistent keywords, taken from your most profitable Search campaigns. A segment that mixes “payroll software” and “Christmas gifts” describes nobody.
- Add 5 to 15 URLs of reference sites, including comparison sites or specialist media.
- Check the size estimate shown on the right: below 10,000 weekly users, delivery will be limited; beyond several million, the segment is too vague.
Name the segment with its logic and the date (“Intent – payroll software – 2026-09”); an account quickly builds up dozens of segments that cannot be told apart. SEA audits regularly turn up segments created three years ago, never updated and still active.
Which campaigns is the segment useful in?
| Type of campaign | Role of the segment | Recommended use |
|---|---|---|
| Search | Observation only, with a possible bid adjustment | Measure whether visitors in the segment convert better, then adjust by +10 to +30% |
| Display | Direct targeting | Prospecting on an identified intent, alongside remarketing |
| Video (YouTube) | Direct targeting, with the “terms searched on Google” option | Reach those who searched your keywords in the last 7 to 30 days |
| Demand Gen | Direct targeting | The best-performing use case in 2026 for demand generation |
| Performance Max | Audience signal (an indication, not a restriction) | Speed up the learning phase; Google will then broaden out |
In Performance Max, the segment is only a suggestion. It steers the first days of delivery, then the algorithm targets whoever it wants. Do not count on it to exclude an audience: exclusions go through other settings, described in the objectives of a Google Ads campaign.
Combining it with other audiences
A custom segment on its own is rarely enough. The combinations that give measurable results:
- Custom segment and exclusion of converters: avoids paying for impressions on existing customers.
- Custom segment crossed with a demographic criterion: the “AND” operator of combined segments restricts to an age bracket or a parental status, useful for local services.
- Custom segment and a remarketing audience in observation: the first prospects, the second measures renewed contact; see remarketing strategies.
- Custom segment and customer list (Customer Match) as a lookalike: since similar audiences ended in 2023, the list acts as a signal in automated campaigns, and the custom segment brings the intent side.
Measuring whether the segment works
Each campaign’s Audiences report shows impressions, clicks, conversions and cost per conversion by segment. Compare over at least 30 days: a custom segment that costs 20% more per conversion than remarketing is normal (it is prospecting); a segment that costs three times more needs tightening. Also check the engagement rate in GA4 for traffic from the campaign, isolating the source through the auto-tagging parameters; the report Ads performance in GA4 describes how to read it. The CPCs observed in France in 2026 on Display with a custom segment sit between €0.20 and €0.80 depending on the sector, against €0.10 to €0.40 with no targeting: the extra cost is only justified if the conversion rate follows.
The mistakes that strip the segment of its meaning
- Adding competitors’ brand keywords thinking you will target their customers: the segment becomes a mix of the curious, job applicants and providers.
- Copying the 200 keywords from the Search campaign: the segment loses all consistency and Google treats it as a broad audience.
- Leaving optimised targeting on without knowing it: in Display, it broadens the segment automatically; turn it off if you want to test the segment as it is.
- Judging over one week: intent audiences take 2 to 3 weeks to gather enough conversions to be compared.
How GreenRed helps
Rather than juggling several tools, GreenRed's Google Ads module brings these metrics together in a single dashboard, compares them over time and tells you which actions come first. You can try it free, with no card, from the Pricing.
Frequently asked questions
What is the difference between a custom segment and an in-market audience?
In-market audiences are categories predefined by Google (for example “car insurance”), identical for every advertiser. A custom segment is defined by your own keywords and URLs, so it fits a specific offer. The first is broader and simpler; the second is finer but has to be built and maintained.
Does a custom segment work in a Search campaign?
Not as direct targeting. In Search, custom segments can only be added in observation: the campaign carries on delivering on the keywords, and you see the segment’s performance separately, with the option to adjust the bid. That is useful for validating an intent before using it in Display or Demand Gen.
How many keywords should you put in a custom segment?
Between 10 and 30 terms close to one another, taken from the queries that already convert in your Search campaigns. Beyond that, the segment loses its consistency and Google treats it as a general audience. Below 10, the size estimate is often too small to deliver regularly.
Do custom segments comply with the GDPR?
They rely on the data of users signed in to Google and on the consent collected by Google, not on your site’s data. You have nothing to collect. On the other hand, as soon as you cross a segment with remarketing or a customer list, consent on your site and consent mode become necessary.