How Google Ads Actually Uses Website URLs in Custom Segments

By: Jyll Saskin Gales, Google Ads Coach

When building a Custom Segment in Google Ads, advertisers face a common but crucial question: how specific should you be with the website URLs you provide? Should you use a full, deep-link URL? A specific sub-page? Or just the main domain?

The vagueness of Google's guidance often leads to confusion, but the functional answer is clear: you should always focus on the top-level domain.

Understanding the logic behind this is essential. Using the right inputs from the start will lead to sharper, more effective audiences, while getting it wrong can lead to wasted time and poorly defined targeting. This guide will break down why the domain is the key signal and introduce the critical strategy of "audience triangulation" to maximize your results.

Remember, The Domain is the Signal, Not true Targeting

When you enter example.com/specific-page into a Custom Segment, the algorithm almost certainly ignores the /specific-page part and focuses solely on the core domain: example.com. There are two fundamental reasons for this.

1. The "Similar To" Principle

First, it's crucial to understand that the system's goal is to find users who browse websites similar to the ones you provide, not the visitors of that single URL. The algorithm is looking for broader behavioural patterns and thematic connections. It analyzes the content and audience of example.com as a whole to build a profile of the type of person who visits it, then finds other users across the web with overlapping interests and Browse habits.

2. The Data Access Reality

Second, for privacy and technical reasons, Google Ads does not have access to granular, page-level visit data across the entire third-party web for the purpose of building advertising audiences. While a website owner using Google Analytics can see which specific pages users visit on their own site, that data is not fed into a universal pool for ad targeting. The system can identify the kind of user that visits example.com, but it likely can't (or won't) distinguish between someone who saw the "shoes" page versus the "dresses" page.

The Power of Triangulation: Why More is Better with Custom Segments

Because the algorithm is building a thematic profile, providing a single website is not enough. To create a truly effective Custom Segment, you must provide a range of examples. I recommend that you input 5 to 10 different but related website domains.

Think of this as audience triangulation.

Imagine a detective in your favourite TV show trying to find a suspect by tracking their cell phone. A single ping from one cell tower only provides a wide, general radius. It's imprecise. But when the phone pings off multiple towers from different locations, the detective can triangulate the signals to pinpoint the suspect's exact location with incredible accuracy.

Building a Custom Segment works the same way.

• One Website: Giving Google just one website is like that single ping. Not useful.
• Multiple Websites: Giving Google 5-10 thematically similar websites allows it to "triangulate" the signals. It analyzes the overlapping audience characteristics of all the sites you provide - for example, The Wall Street Journal, Bloomberg, and The Economist for a news-focused segment - to create a much sharper, more accurate profile of the exact user you're trying to reach.

Best Practices for Custom Segments Website Inputs: A Summary

To make this simple, follow these two rules when adding website URLs to your Custom Segments:

1. Always Use the Top-Level Domain: Ignore specific pages and subdomains. Input websitename.com, anotherone.org, etc.
2. Provide a Diverse List (5-10): Don't rely on a single example. Give the system multiple data points so it can effectively triangulate your ideal customer profile.

By understanding that your goal is to feed the algorithm thematic examples, not to target visitors of a specific page, you can build more intelligent Custom Segments and connect with the right audience with far greater precision.