Allowlist

An allowlist is a list of values that are permitted. Everything else is out. In remnant buying the word usually attaches to exchanges (inventory_source), sites, or apps you will bid on.

That is the opposite of a blocklist. A blocklist removes named junk and leaves the rest eligible. An allowlist must restate every value you still want. If you drop one exchange from an allowlist, you are not "excluding a name." You are rewriting the whole permitted set.

On this product, inventory-source targeting is an allowlist. Subtracting an exchange means listing the others. If no explicit list exists, a Supply Audit apply can fall back to exchanges observed on a covered run, and it will say that reach narrowed from unrestricted. An apply that would leave the list empty is refused, because an empty allowlist compiles to an expression that matches no inventory. The next campaign would not serve.

Do not confuse "we did not set an allowlist" with "we curated the open web." Unset means unrestricted remnant, not a careful list.

See why an empty allowlist serves nothing when you need the operational failure mode.