Ad Refresh Without Wrecking Your CPMs: Best Practices

Ad refresh — reloading an ad slot during a single pageview — can add 20–40% more impressions on long-engagement pages. Done crudely, it also tanks your CPMs, angers buyers and risks policy trouble. The difference is entirely in the trigger logic.

Why naive refresh backfires

A 30-second timer refreshes ads nobody is looking at: background tabs, abandoned sessions, slots scrolled out of view. Buyers' algorithms notice within days that your impressions convert worse, and they bid down your whole domain — not just the refreshed units. You gained impressions and lost price across the board.

The professional refresh checklist

• Trigger on viewability, not time alone: refresh only slots that are 51%+ in view with recent user interaction (scroll, click, touch).
• Respect tab focus: never refresh hidden tabs.
• Cap per session and per buyer: 3–5 refreshes per slot is a sane ceiling; some PMP buyers contractually require first-impression-only.
• Declare it: Google requires refreshed inventory to be declared in GAM. Undeclared refresh risks demand restrictions.
• Refresh-aware floors: later refresh impressions are worth less; price them on their own curve instead of letting them drag your primary floors down.
• Exclude high-value formats: video, takeovers and direct-sold campaigns usually shouldn't refresh.

Measure decay honestly

Report refresh impressions as a separate dimension. A healthy setup shows first impressions at, say, $2.60 and refresh impressions at $1.40–1.90 with stable fill. If refresh CPMs sit below 40% of first-load, your intervals are too aggressive or your viewability trigger is broken.

Let the machine tune intervals

The optimal refresh interval differs by placement, geo, session depth and even time of day. This is a textbook machine-learning problem: explore intervals against a holdout, keep what wins. PubMonetX's Smart Refresh runs that experiment loop continuously per placement, so refresh stays accretive instead of cannibalistic.