Meta Ads Lookalike Audience: what it is and how to build one
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Lookalike audiences are one of the most powerful tools in Meta Ads, but most are built wrong. Here's which source to use and what size works in Romania.
What Is a Lookalike Audience
A Lookalike audience is created by Meta's algorithm based on a source group you define. Meta analyses the demographic profile, behaviours and interests of people in your source and finds similar users on Facebook and Instagram - people who don't know you exist but share the profile of your best customers.
The logic: instead of manually selecting interests like "fitness enthusiasts aged 25-45", you give Meta a list of real people who already bought from you, and let the algorithm identify the patterns it can't articulate but can detect.
Source Quality Is Everything
The Lookalike is only as good as the source. Best sources in order of quality:
- Repeat buyers (2+ purchases) - highest quality signal, these are your actual best customers
- Top 25% customers by LTV - if you have CRM data, use it. A Lookalike based on high-LTV customers finds more high-LTV customers
- All buyers (Purchase event) - good if you have minimum 1,000 buyers in the source. Below 1,000 the signal is weak
- Add-to-cart visitors - high intent but unconverted. Useful if you don't have enough buyers
- Facebook page fans - avoid. Fans are not customers; many liked the page from contests or paid boosts
Audience Size: 1%, 2% or More?
Lookalike size is expressed as a percentage of the selected country's population. In Romania:
- 1% ≈ 80,000-100,000 people - most similar to source, most expensive to reach
- 2% ≈ 160,000-200,000 - good balance between similarity and volume
- 5% ≈ 400,000 - less similar but cheaper per impression
- 10% ≈ 800,000 - almost a broad audience, similarity is diluted
Our recommendation for the Romanian market: start with 1-2% and test. If frequency exceeds 3-4 in 7 days, expand to 3-5%.
When Lookalike Works and When It Doesn't
Works well when: you have minimum 500-1,000 people in the source (ideally 1,000+), the source is homogeneous (all buyers, not a mix of visitors and buyers), and your product has broad demand.
Doesn't work well when: the source has fewer than 100 people, the source is polluted (newsletter subscribers who never purchased, page fans), or your product has an extremely specific ICP that Meta can't detect from online behaviours.
Why Lookalike Is Harder to Manage Than It Looks
Meta has introduced Advantage+ Audiences, which combines lookalikes with algorithm-controlled targeting. The dilemma is real: if you give the algorithm full control, you don't know who you're targeting and can't interpret results. If you maintain manual Lookalike, you risk limiting distribution at a moment when the platform sees signals you don't have.
The right answer depends on data from your specific account, the size of source audiences, and campaign history. There's no universally optimal configuration. And properly testing both approaches requires sufficient budget and several weeks of clean data, with no parallel creative changes that would distort the conclusion.
Frequently asked questions
What is Lookalike Audience on Meta Ads?
Lookalike Audience is a Meta Ads feature that lets you reach new users who resemble your existing customers. Meta analyzes the demographic characteristics, behaviors, and interests of your source audience and identifies similar people on Facebook and Instagram. It's one of the methods with the best CPA for prospecting.
What source should I use to create a Lookalike Audience?
The best sources, in order: 1) Customer list with email addresses and phone numbers of existing customers. 2) Meta Pixel with purchase event (buyers, not just visitors). 3) Product page or checkout visitors. A more qualitative source (real customers) produces a better-performing Lookalike than a larger but more diluted source.
What Lookalike size should I choose: 1%, 3%, or 10%?
Lookalike 1% = most similar to your source, smaller but more relevant audience. Lookalike 10% = larger but less precise audience. Start with 1-2% for efficient prospecting. If the audience exhausts itself (high frequency), expand to 3-5%. Lookalike 10% makes more sense for awareness campaigns at large budgets.
Does Lookalike Audience still work after iOS 14 and privacy changes?
It works less precisely than before iOS 14, but remains one of Meta's best tools for prospecting. Apple's privacy changes reduced Pixel-available data, which diluted the quality of mobile event-based Lookalikes. The solution: use Customer Lists from your CRM as the primary source - these are not affected by iOS 14.
Should I exclude existing customers from a Lookalike Audience campaign?
Yes, always. If you don't exclude existing customers, you spend prospecting budget on people who already bought - they should be targeted with remarketing or retention campaigns, with different messages and usually lower costs. Create a Custom Audience with existing customers and add it as an exclusion in Lookalike campaigns.
At DAFE Digital we build Lookalike audiences calibrated on your real customers. Controlled expansion, not random traffic.
A good Lookalike audience depends on the quality of the source list and the chosen size. We build sources from the correct data and test sizes so expansion brings new customers similar to your best ones.
Adela Mincea
Performance Marketer · Fondatoare DAFE Digital · Formator ANC
Adela is a Performance Marketer with 10+ years of paid media across Europe, the US and Asia. She founded DAFE Digital in 2023 after agency roles in London and Hong Kong, in-house work inside client organisations, and independent consulting across 27+ industries.
