Improving Your CPMs

Seven actionable steps to increase your effective CPMs — optimising placement for viewability, using the right ad sizes, fixing ads.txt, maximising consent, and improving page performance.

CPMs are the product of many interacting factors — placement quality, audience, demand competition, and technical setup. This article covers the most impactful things you can do to increase your effective CPMs.

1. Optimise ad placement for viewability

Viewability is one of the strongest signals demand partners use to price inventory. Ads that are consistently seen command higher bids.

Place ads above the fold or within content. A leaderboard at the top of the page or a mid-article rectangle typically outperforms a footer or sidebar ad on viewability, and therefore CPMs.
Avoid placing ads in tabs, collapsed accordions, or hidden sections. These never become viewable and will drag down your average.
Pre-reserve slot height. Add a min-height equal to the tallest ad size to the slot's container. This prevents layout shift when the ad loads and keeps the ad in its intended position rather than being pushed off-screen by content loading above it. See Layout Shift (CLS) Issues.

2. Use the right sizes for each placement

Larger ad sizes generally command higher CPMs because they offer more creative canvas to advertisers. But size alone is not the answer — a large format in a poor position still underperforms.

Placement	Recommended sizes
Leaderboard (top of page)	728×90, 970×90, 970×250
Mid-content rectangle	300×250, 336×280
Sidebar	300×250, 300×600, 160×600
Mobile top / in-content	320×50, 320×100, 300×250
Sticky footer	728×90, 320×50 (auto-selected by viewport)

Enable multiple sizes per slot. Advlume's responsive size mapping will automatically serve the correct size for each visitor's viewport.

3. Ensure your ads.txt is correct and up to date

DSPs that cannot verify your inventory against ads.txt will either suppress their bids or apply a significant price penalty. An incorrect or outdated ads.txt is one of the most common causes of unexpectedly low CPMs.

Download your latest personalised ads.txt from Settings → ads.txt and re-upload it to your domain root whenever you see a warning in GAM. See ads.txt Setup Guide.

4. Maximise consent rates

Visitors who grant consent for personalised advertising are worth significantly more to demand partners. In the EEA, a typical CPM uplift of 3–6× is common between non-consented and consented traffic.

Make sure the consent banner is visible and not obscured by other elements.
Do not auto-dismiss or pre-tick the consent dialog — this is against IAB policy and will result in invalid consent strings that reduce rather than increase demand.
A well-designed, trustworthy-looking consent prompt with a clear "Accept" button typically achieves 60–80% consent rates.

5. Improve page load performance

Prebid has a 1,500ms timeout. If your page is slow to load, demand partners' bid requests may time out before their responses arrive, reducing competition and fill. Target a page load time (Time to Interactive) under 3 seconds.

Compress images (WebP/AVIF) and defer non-critical scripts.
Use a CDN for static assets.
Keep third-party scripts to a minimum — each one adds network round-trips.

6. Build a quality audience

User demographics and engagement signals are the strongest long-term drivers of CPM. Traffic from high-income English-speaking countries (US, UK, CA, AU) commands CPMs 3–10× higher than equivalent traffic from tier-3 geos. Returning, engaged visitors attract retargeting budgets. One-time or bounce traffic earns less.

Invest in SEO and direct traffic over arbitrage-sourced traffic. Organic audiences are more valuable to advertisers.
Publish high-quality content in categories with strong advertiser demand: finance, technology, health, and travel typically have the best CPMs.
Build a newsletter or push notification list to grow direct return visitors.

7. Check the demand channel breakdown

In your Revenue Report, look at the per-channel eCPM column. If one channel is significantly outperforming others at high impression share, it may indicate that other channels are under-bidding on your inventory. Contact your account manager to discuss whether additional bidder configuration could increase competition.