What are Custom Audiences?
A Custom Audience is a user-defined target group that you create yourself on advertising platforms such as Google Ads and Meta. You specify the data points that describe your ideal customer, and the platforms’ algorithms then use those signals to find and engage users who resemble them. This allows you to build your target audience based on actual behavior patterns and interests, rather than broad categories like “sports fans” or “parents of young children.”
In practice, Custom Audiences combine intent (what people search for and do) with interest (what they engage with). Google has combined the previous types—Custom Intent and Custom Affinity—into a single solution that can be used across campaign types such as Display, YouTube, or Performance Max. Meta has its own version, where you can upload customer lists or segment visitors to your website based on actions or time spent on the site. In both cases, this gives you far more precise control over who sees your ads and at what point in the customer journey they encounter them.
How do you use Custom Audiences?
You create a Custom Audience by selecting the signals that best describe your target audience. In Google Ads, this is done in Audience Manager, where you define keywords, URLs, or apps that reflect your target audience’s behavior. The system then analyzes which users match this profile and continuously adjusts the reach depending on whether your campaign is designed to drive awareness, consideration, or conversions.
On Meta, it works a little differently because you often base your target audience on first-party data. If you upload email addresses, they form the foundation for a Custom Audience, which you can expand with lookalike segments. Alternatively, you can build your audience based on website behavior—for example, people who have added items to their cart but didn’t complete the purchase. This allows for targeted retargeting in your SEMor social media strategy without relying entirely on the platforms’ broad algorithmic targeting.
Example of creating a Custom Audience:
2. Select “Custom segment” and enter 10–15 relevant keywords
3. Add 3–5 URLs based on websites your target audience visits
4. Select apps that your target audience uses
5. Apply the audience to Display or YouTube campaigns
That's why you should use Custom Audiences
Custom Audiences provide better match quality than predefined categories because you base them on your own insights. You know your market best, and with the platforms’ data, you can combine that knowledge with machine learning. This makes your ads more relevant, which typically results in lower cost per conversion and fewer impressions to users who wouldn’t buy anyway.
If you work with digital strategy, Custom Audiences is a key tool for aligning your brand strategy with your performance goals. You use the same approach whether you’re driving traffic through Google Ads, paid social media, or an integrated Performance Max setup. This creates a common thread between the performance of your channels and your overall marketing efforts, regardless of the format.
What types and varieties are available?
Custom Audiences encompass several types, depending on the signals you use to build the audience. In Google Ads, the main sources are keywords, URLs, and apps, while Meta offers four main data sources: customer lists, website behavior, purchase history, and app activity. You can also combine signals—for example, keywords from Google and web data from your own cookies—to create a more holistic picture of your target audience.
In addition, you can create competitor-based segments to target people who visit competitors’ websites or use their apps. However, this requires careful thought and ethical consideration, because targeting competitors can quickly lose its effectiveness if the signals aren’t high-quality enough. Therefore, use Custom Audiences as a precision tool—not as a shortcut to reaching “everyone.”
How do you use Custom Audiences in practice?
The most effective approach is to work in a structured manner and test continuously. Start with narrow segments and expand only once you see consistent performance. You can measure the impact using classic KPIs such as CTR, conversion rate, and ROAS. Compare figures from your Custom Audiences with results from the platform’s predefined segments—you’ll often find that relevance and engagement increase because the data sample is a better fit for your product.
Example of a segmentation strategy:
– Combine audience data from Meta (e.g., users who have watched a video) for cross-platform remarketing
– Exclude irrelevant search terms such as “free” or “cheap” to refine your target audience
– Build lookalike audiences based on high-value customers in the CRM system
If you’re also working on SEO or content creation, you can use the same keywords from your audience structure as inspiration for organic content. This ensures that your paid and organic strategies support one another and speak to the same personas. That way, you’ll leverage your advertising data as insights for your entire marketing ecosystem, rather than just your campaigns.
What should you keep in mind?
First and foremost, you must ensure GDPR compliance if you upload personal data such as email addresses or phone numbers. You are the data controller, and the platforms act as data processors. Therefore, make sure you have valid consent and clear documentation of how the information is used. Also, avoid using customer lists that are too small, as this can introduce bias in your targeting or render your campaign ineffective.
Furthermore, automation can sometimes compromise the accuracy of your Custom Audiences, especially if you mix too many signals. Stay focused on your goal—are you aiming for reach or conversions? The clearer your structure is, the better the AI responsible for matching will perform. This applies across all platforms, whether you’re running Google Ads, Meta, or working with paid social campaigns. In short, a well-defined Custom Audience is the key to getting the full return on your digital investments.
