Glossary

Traffic-back URL

A traffic-back URL (also called fallback or default URL) is where an ad server sends a visitor when no campaign can serve the request — every eligible campaign is over its cap, out of budget, or the visitor matches no targeting. Instead of a dead end, the click is redirected somewhere that can still monetize it.

How it works

The traffic-back URL is configured per zone. On an unfillable request the server answers with a redirect to it — often a smartlink, a house offer, or a partner's feed that accepts remnant traffic. Trackers usually mark such events separately (fallback rather than impression), so unsold volume is visible in reports without polluting campaign stats or billing.

Why it matters

For publishers and networks, traffic-back is the difference between wasted and salvaged inventory: capped campaigns still leave every extra visitor with somewhere to go. Watching the fallback share per zone is also a cheap health metric — a spike means caps, budgets, or targeting are choking demand.

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