Custom Audiences vs Lookalike Audiences (Simple Explanation)
Custom Audiences vs Lookalike Audiences (Simple Explanation)
Introduction
Custom audiences and lookalike audiences are two of the most commonly used audience types in social media advertising. They are often mentioned together, but they serve very different purposes and are used at different stages of a campaign.
If you are new to audience targeting — or if you have heard these terms but are not fully clear on how they differ — this guide provides a simple, plain-English explanation. By the end, you will understand what each audience type is, how they work, and when you should use one over the other.
What Is a Custom Audience?
A custom audience is built from people who have already interacted with your brand in some way. Instead of targeting strangers, you are targeting users who are already familiar with you.
Custom audiences are built from people who have already interacted with your brand in some way, such as website visits, email subscriptions, or past purchases. If you want a deeper breakdown of how these audiences are created and used across platforms, see our guide on what social media custom audiences are and how they work.
Common sources for custom audiences include:
-
Website visitors
-
Email subscribers
-
Past customers
-
App users
-
People who engaged with your social media content
Because these users already have a connection to your brand, custom audiences are often used for retargeting and high-intent campaigns.
In simple terms, custom audiences allow you to re-reach people you already know.
What Is a Lookalike Audience?
A lookalike audience is created by a platform (such as Facebook or Instagram) using machine learning. The platform analyzes a source audience — often a custom audience — and finds new users who share similar characteristics and behaviors.
For example, you can create lookalike audiences based on:
-
Existing customers
-
High-value purchasers
-
Engaged website visitors
-
Email subscribers
Lookalike audiences are primarily used for prospecting and scaling, helping advertisers reach new users who are likely to behave similarly to their best customers.
In simple terms, lookalike audiences help you find new people who resemble the ones you already have.
The Core Difference Between Custom and Lookalike Audiences
The main difference comes down to data source and intent.
-
Custom audiences use your existing data
-
Lookalike audiences use modeled data generated by the platform
Custom audiences are made up of users who already know your brand, while lookalike audiences are designed to introduce your brand to new people.
Because of this, custom audiences typically perform better for conversions, while lookalike audiences perform better for reach and growth.
When Should You Use a Custom Audience?
Custom audiences work best when your goal is to convert or re-engage users who already showed interest.
Many advertisers use pre-built custom audience segments to speed up campaign setup and ensure consistent targeting. For example, you can explore ready-to-use Facebook custom audience segments designed for common behavioral and interest-based targeting scenarios.
Typical use cases include:
-
Retargeting website visitors
-
Re-engaging past customers
-
Upselling or cross-selling
-
Abandoned cart campaigns
These audiences are usually smaller in size but higher in intent, which often leads to stronger conversion rates.
When Should You Use a Lookalike Audience?
Lookalike audiences are best used when you want to expand beyond your existing audience.
Common use cases include:
-
Scaling successful campaigns
-
Reaching new customers
-
Growing brand awareness
-
Filling the top of the funnel
While lookalike audiences are larger and offer more reach, their performance depends heavily on the quality of the source audience used to create them.
Common Beginner Mistakes
Many advertisers make avoidable mistakes when using these audience types for the first time.
Some of the most common include:
-
Using lookalike audiences before building strong custom audiences
-
Using outdated or low-quality source data
-
Expecting lookalikes to perform like retargeting audiences
Understanding the strengths and limitations of each audience type helps prevent wasted ad spend.
Quick Summary: Custom vs Lookalike Audiences
Custom audiences and lookalike audiences are not competitors — they are complementary tools.
Custom audiences help you reconnect with people who already know your brand, while lookalike audiences help you reach new users who share similar traits. Most successful campaigns use both together as part of a broader audience strategy.
For a deeper breakdown of costs, examples, and advanced use cases, see our full comparison guide. This article provides a simple overview of the differences, but if you want a more detailed comparison — including real-world examples, cost considerations, and advanced use cases — read our full guide on custom audiences vs lookalike audiences, with examples and costs.
Frequently Asked Questions
What is the main difference between custom audiences and lookalike audiences?
The main difference is the data source. Custom audiences are built from people who have already interacted with your brand, while lookalike audiences are created by platforms to find new users who resemble those existing audiences.
Which audience type should beginners use first?
Most beginners should start with custom audiences if they have existing data, such as website visitors or email subscribers. Custom audiences are more predictable and easier to optimize before expanding into lookalike audiences.
Are custom audiences better than lookalike audiences?
Neither is inherently better. Custom audiences are usually more effective for conversions and retargeting, while lookalike audiences are better for scaling and reaching new users.
Can custom audiences and lookalike audiences be used together?
Yes. Many advertisers use custom audiences for retargeting and lookalike audiences for prospecting. Using both together helps cover different stages of the marketing funnel.
Do lookalike audiences always perform well?
Lookalike audience performance depends heavily on the quality of the source audience. Poor or outdated source data can lead to weak results, even if the lookalike audience is large.
How often should custom audiences be updated?
Custom audiences should be refreshed regularly, especially if they rely on time-sensitive data such as website visits or recent purchases. Fresh data improves accuracy and performance.