Every advertiser who's run a flash sale on Google has lived this: you discount 25%, conversion rates spike, and Smart Bidding panics. ROAS drops in the first few hours, the algorithm reads it as declining performance, pulls spend back, and by the time it recalibrates the peak window has shrunk. You've paid full CPCs during a sale you designed to generate volume.
Google's seasonality adjustments existed for this — a manual signal warning the algorithm that conversion rates were about to change. But they only adjusted conversion rate predictions. They didn't let you touch the ROAS target itself, or pre-commit extra budget to the window.
Promotion Mode does both.
What the new beta actually lets you do
Google Ads Liaison Ginny Marvin announced Promotion Mode beta on June 16, alongside two other bidding updates. Available now for Search and Performance Max campaigns, it gives you two controls that activate on a scheduled start date:
A ROAS tolerance adjustment — you tell the algorithm what floor you're willing to accept during the window, in exchange for going after more volume. If your normal ROAS target is 400% and you're fine with 280% during Prime Day in exchange for significantly more conversions, you can encode that decision in advance.
An extra daily budget layer — so the campaign doesn't hit its standard cap at 11am and go dark during the most competitive hours of the event. This extra budget works with both daily and total campaign budgets.
You set the window, the floor, and the increment before the event starts. The system switches modes when the clock hits your start date. No manual override required on June 23 morning.
Smart Bidding Exploration is also expanding today
Also announced June 16: Smart Bidding Exploration — which widens query targeting to find conversions from searches your campaign currently ignores — is now available for PMax campaigns without product feeds, and entering beta for Standard Shopping campaigns.
Google's cited numbers for accounts using the feature: 18% more unique converting search query categories, 19% more total conversions. The mechanic requires setting a ROAS tolerance that allows the algorithm to chase lower-probability queries that still convert often enough to justify the bid.
Worth saying directly: this is most useful for accounts that have hit a performance ceiling with tight targets. If your campaigns are already struggling with profitability, widening the query net without improving economics makes the problem larger.
The Shopping beta is also worth treating carefully this week. Running a new beta feature inside your Prime Day campaigns is a bad idea. Test Smart Bidding Exploration in Shopping separately, after the event.
What to actually set up before June 22
Promotion Mode is in beta, which means it's not in every account yet. In Google Ads, open a Search or PMax campaign, go to Settings, find Bidding, and look for the Promotion Mode option.
If it's available:
- Set your window: June 23, 12:01 AM to June 26, 11:59 PM (local timezone)
- Define your ROAS floor: be honest here — 300%? 250%? Whatever number means the event was worth running
- Set your budget increment based on actual 2025 Prime Day data or realistic seasonality estimates, not an optimistic stretch target
- Verify the setup is live before June 22, not June 23
If Promotion Mode isn't showing up in your account yet, the existing Seasonality Adjustments tool (Tools in the top nav > Bidding adjustments > Seasonality adjustments) still works. It covers the conversion rate prediction signal without the ROAS target flexibility — a partial version of the same fix.
The August 17 change worth noting separately
The third update from June 16: starting August 17, "Bidding Target Optimization" for budget-constrained campaigns changes to deliver more predictable performance with fixed spending limits. Google Ads will show notifications about this starting July 6, with a prompt to review historical campaign performance before the change kicks in.
This one has nothing to do with Prime Day. It's relevant in Q3 for anyone running total-budget campaigns — the structure of how Google handles constrained budgets is changing, and you'll want to understand the difference in your account before August rolls around.
Gromerce's free audit shows how your current bidding configuration handles demand spikes — if Prime Day is a meaningful event for your brand, running the audit takes three minutes and surfaces the gaps before June 23.
Smart Bidding's biggest limitation has always been that it optimizes for averages, not for the one week a year when all your economics change at once — Promotion Mode is a tool worth having in the calendar before the window opens.
Sources: Ginny Marvin via LinkedIn, Search Engine Journal, Search Engine Land, June 2026
