A Google Ads custom segment built from competitor URLs doesn't target the people who visited those sites. For the "People who browse websites similar to" option, Google says your ads will reach people who browse websites similar to the URLs you enter, and that this doesn't mean your ads will show on those URLs. The URLs describe your buyer. They aren't a list of your competitor's visitors, and in Performance Max they are only a signal.
What the URL option does
Custom segments are built from three kinds of input, per Google's About custom segments page:
- Keywords, read either as interests or purchase intentions (the default) or as terms people searched on Google properties such as Google.com and YouTube.
- URLs: people who browse websites similar to the ones you enter.
- Apps: people who download and use apps similar to the ones you enter.
Google also says the segment picks an audience focused on reach, consideration or performance based on your campaign goals and bidding strategy. The same list can behave differently in two campaigns.
On a mentoring call, a tutor who prepares students for a physics olympiad asked whether he could show ads to people who had browsed the olympiad's website in the past 30 days without searching for it. The URL option is the closest tool, but Google's page describes no lookback window and no visitor match. You describe the audience, and Google decides who fits it. We also pointed him to the apps option, since a few small prep apps exist for the exam.
Where you can use it
Google lists Display, Gmail, Demand Gen and Video campaigns as places to add a custom segment. Display is moving into Demand Gen, which we cover in what doesn't survive the move. Performance Max is the exception: Google says custom segments can't be applied to it directly, so you add one inside an audience signal on the asset group. Google's audience signals page adds that Performance Max may show ads to relevant audiences outside your signals. That's the same limit behind why PMax can't do pure retargeting.
How we use it
Competitors. In an account we run against UK and German competitors, the Performance Max asset group carries competitor names as search themes and a custom segment built from those competitors' websites. Search alone only reaches people who type a competitor's name. The URL segment describes people researching the same category who never do. It's the competitor campaign in our three-campaign B2B setup, and if your competitors have apps, add those too.
Intent with no clean keyword. On another call, an advisor who helps owners prepare their businesses for sale found that "succession planning" searches skewed toward HR content. Our suggestion was a Performance Max campaign signaled with the websites of executive search firms, where companies go when they need a new head of product, sales or marketing before a sale. The advisor pointed out that owners also visit brokerage and listing sites, which fit the same approach. We preferred that to putting the advisor's face on YouTube for this audience.
What to expect from it
You can't check whether a competitor's customers saw your ad, so judge the segment on the leads it brings. If they don't look like your buyer, tighten the URLs to sites only your buyer would visit. More controls are in our Performance Max guide.
The takeaways
- The URL option reaches people who browse websites similar to the ones you enter. It isn't a visitor list, and ads don't run on those sites.
- Custom segments go straight into Display, Gmail, Demand Gen and Video campaigns. In Performance Max they only work inside an audience signal.
- Performance Max can serve outside its signals, so the segment is a starting point, not a fence.
- Pair competitor URLs with competitor search themes, and use niche-site URLs when your buyer's intent has no clean keyword.
Common questions
Can I target people who visited my competitor's website on Google Ads?
Not as a list of their visitors. A custom segment using the 'People who browse websites similar to' option reaches people who browse websites similar to the URLs you enter, according to Google's About custom segments page. Google also notes that this doesn't mean your ads will show on those URLs. Entering competitor URLs describes the kind of person you want, and Google builds the audience from there.
Which campaign types support custom segments?
Google lists Display, Gmail, Demand Gen and Video campaigns. Custom segments can't be applied directly to Performance Max, because it doesn't have traditional audience targeting. You can add a custom segment inside a Performance Max audience signal instead. Google is also moving Display campaigns into Demand Gen, so new Display builds now start there.
Does a custom segment restrict who sees my Performance Max ads?
No. Audience signals are suggestions that help Google's AI optimize. Google's audience signals page says Performance Max may show ads to relevant audiences outside your signals if they have a strong likelihood of converting. The segment points the campaign at a starting audience. It doesn't fence it in.
What are the custom segment input options?
Keywords, URLs and apps. Keywords can be read as interests or purchase intentions (the default) or as terms people searched on Google properties such as Google.com and YouTube, which only applies on campaigns running on Google properties. URLs reach people who browse similar websites, and apps reach people who download and use similar apps.
Can I share a custom segment across Google Ads accounts?
No. Google says custom segments are not shareable from one account to another, and manager accounts don't show a custom segments table in Audience manager. Build the segment in each account that needs it.