The two levers
A lookalike has exactly two inputs, and both decide its quality. The seed is the source customer list you feed it; the lookalike inherits that list's quality exactly, so a small, clean list of real buyers produces a far better audience than a large, noisy one. The audience size is how wide you cast: 1% is the slice of the targeted population most similar to your seed, and each step up toward 20% adds reach while loosening the resemblance.
How to use it
For quality-led lead generation, start tight at 1% to 2% off a high-intent seed and widen only once you have exhausted it, watching lead quality as you go. It pairs naturally with retargeting in a full-funnel setup, and it is only as trustworthy as the pixel or CAPI signal feeding the seed. We work through the trap in a lookalike only copies the seed you feed it.
Common questions
What percentage should a lookalike audience be?
For quality, start at 1% to 2%, the closest match to your source. Larger percentages such as 5%, 10%, or up to 20% reach more people but resemble your source less, so they suit scaling for volume rather than precision.
Why is my lookalike audience low quality?
Usually the seed. A lookalike copies whatever list you built it from, so a noisy or low-intent source produces a low-intent audience at scale. Rebuild it from a clean list of your real, high-value customers.