A whitelist is a restricted list of the only sources, placements, sites, apps or zones a campaign is permitted to run on, chosen because they have a proven record of quality traffic and conversions.
Definition
A whitelist is a restricted list of the only sources, placements, sites, apps or zones a campaign is permitted to run on, chosen because they have a proven record of quality traffic and conversions. It is the positive counterpart of a blacklist and, on open-inventory networks, it represents the end state of source optimisation: after wide testing establishes which zones produce value, the buyer locks spend to those and scales bids there instead of continuing to pay for exploration across the whole pool.
Running to a whitelist changes the campaign's risk and volume profile. Cost per result usually drops and becomes more predictable because the fraudulent and dead zones are gone, but total available volume is now capped by how much traffic those specific zones can supply, and the buyer is exposed to fatigue — a whitelist of a dozen zones will saturate faster than the open pool.
So whitelisting is a trade of scale for efficiency, appropriate once a campaign is profitable and the goal is to maximise margin rather than reach.
In context
Whitelists are built from the buyer's own granular data — zone or placement SubID reports showing which sources produced registrations and deposits at acceptable cost — not from generic shared lists, because a zone that converts for one offer and creative may not for another. The list is assembled after enough spend to be confident: a zone needs a meaningful click and conversion sample before it earns a place, and marginal zones are usually kept on a watch tier rather than promoted straight to the whitelist.
Because whitelisted zones fatigue and degrade, buyers do not treat the list as permanent. They rotate fresh creatives through the whitelist to extend its life, periodically re-open a small exploration budget on the open pool to find new winners, and demote zones whose cost per result drifts upward.
A healthy campaign often runs two layers at once: a whitelist carrying most of the budget at scaled bids, and a small testing layer feeding new zones into it.
Worked example
After three weeks of testing across an open native pool, a buyer identifies twelve widgets that together deliver a $48 cost per FTD. They move the campaign to a whitelist of just those twelve, raise bids 30% to win more of their inventory, and run a separate $30-a-day exploration campaign to keep finding replacements as the twelve fatigue.
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