Facebook Lookalike Audiences: Build Them Right
Lookalike audiences are the most powerful cold targeting tool on Facebook. You give it a list of your best customers and it finds millions of people who look like them. The problem is most small businesses build them from the wrong source, which means they find people who look like their worst customers instead.
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What a lookalike audience actually does
Facebook takes your source audience, analyzes hundreds of data points about those people, and finds other Facebook users who share similar characteristics. The result is a cold audience that is statistically more likely to behave the way your source audience behaves. The quality of your lookalike is entirely determined by the quality of your source.
The source audiences ranked by quality
| Source | Quality | Why |
|---|---|---|
| Purchase events from your pixel | Best | Actual buyers: the purest signal of who converts |
| Your customer email list | Excellent | Real customers, especially if segmented by LTV |
| Add-to-cart events | Good | Strong intent, not actual buyers but close |
| Website visitors (all) | Okay | Too broad, includes people who bounced in 2 seconds |
| Page engagers (likes, comments) | Weak | Engagement does not correlate well with purchase behavior |
The minimum source size you need
Facebook requires at least 100 people in your source audience to build a lookalike. But 100 is not enough for a quality lookalike. Aim for 500-1,000 actual customers as your source. Below 500, the lookalike is too noisy. Above 10,000, you get diminishing returns. The sweet spot is 1,000-5,000 people from a high-quality source.
The 1% vs broader lookalike
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When you build a lookalike, you choose a percentage (1-10%). A 1% lookalike is the smallest, tightest match. It is the people most similar to your source. A 5% lookalike is larger but less precise. For most small businesses, start with 1%. Scale to 2-3% when your 1% lookalike is profitable. Go broader only when you have exhausted the tighter audiences.
Build your lookalike from your buyers, not your followers. One list of 500 actual customers beats a million page followers as a lookalike source every single time.
How to update your lookalike
Facebook refreshes lookalike audiences automatically every 3-7 days. But your source custom audience does not update automatically unless you use a pixel event (which updates in real time) or re-upload your customer list manually. Customer list lookalikes should be re-uploaded monthly to stay fresh.
Questions people ask
How many people do I need to create a Facebook lookalike audience?
Facebook requires a minimum of 100 people in your source. But for a useful lookalike, you need at least 500 actual customers. With fewer than 500, the statistical match is unreliable.
What is the difference between 1% and 5% lookalike audiences on Facebook?
1% is the closest match to your source (smallest, most precise). 5% is larger and reaches more people but is less precise. Start with 1% and expand to 2-3% once the 1% audience is profitable.
Should I use interest targeting or lookalike audiences?
For most businesses with enough customer data, lookalike audiences outperform interest targeting. Start with lookalikes if you have 500+ buyers in your pixel or customer list. Use interest targeting only if you are new and have no customer data yet.
Can I use my email list to create a Facebook lookalike?
Yes. Upload your customer email list as a Custom Audience, then build a lookalike from that. Facebook will match your emails to Facebook profiles (typically 40-70% match rate). The better segmented your list (buyers only vs all subscribers), the better the lookalike.