Custom Audiences

A custom audience is a group of people you already know, built from a list you upload or from your own site traffic, that you target or exclude on X.

You upload a file of emails or phone numbers, or you let the X pixel collect your site visitors, and X matches those people to accounts. You can then run ads to that group, or exclude it so your prospecting never wastes budget on people you already have.

Say you upload your 20,000 past customers. X matches around 12,000 of them to accounts, and you run a win-back ad to that group while excluding anyone who bought this month. Check the match count before you plan spend against it.

Match rate decides the real size. Only the people X can match to an account are reachable, so a 20,000-row list can collapse into a much smaller audience. A thin match may be too small to serve at all.

The list you upload is bigger than the list you reach.