As publishers grow their business they become more likely to switch from CPC-based monetization, like AdSense to CPM-based ads. It’s a big step in the publisher journey; marking the point where you have the credibility to sell your advertising based on the quality of the inventory rather than just when an ad copywriter can entice your user to click away from your content.
It’s a change well worth making. Whilst you can only sell one click away from your page you can potentially sell multiple impressions. Impression-based advertising also attracts bigger spending campaigns and allows you to use strategies such as header bidding and open bidding to create price competition.
Viewability is Important
Many CPM-based ads now pay only by viewable impression, i.e. when the ad system measures that the impression has been in the visible part of the viewport for long enough to count. Even straightforward CPM ads are heavily impacted by viewability,, as buyers will bid based on the average viewability of an ad unit.
Place Ads in Front of Users
Different systems measure an ad as viewable based on different criteria. Google uses “Active View”, which for image-based ads means that 50% of the creative was in view for at least 1 second. That 1 second becomes important if ads are placed where users are likely to scroll past them. Ads at the very tops of pages and MPUs mid content on mobile can be in view for disappointingly short times before the user scrolls down.
Placing ads alongside content that users pause to look at or engage with can bring a boost to viewability that supports higher CPMs. Our Content Engagement Unit is perfect for this, but images, polls, and callouts all work well.
Lazy Load Low Viewability Units
Most ad units begin to load as the page starts loading. An alternative that works well on lower viewability units is to only begin loading the unit as the user scrolls closer to where the unit will be displayed: Lazy loading.
Because lazy-loaded units don’t load when the user is never likely to see them, they result in a higher proportion of viewable impressions. When first implemented this can actually reduce revenue as there are fewer impressions. However, as your historic viewability improves the rates you receive for those impressions will improve too.
Vertical Units Perform Better
Vertical units, like sky-scrapers and double-MPUs, are often shunned by those optimizing for clicks. Their natural home on desktop at least is the sidebar where they are easily ignored and don’t attract many clicks. It’s not unusual to see AdSense publishers remove skyscrapers and replace them with in-content MPUs as a result.
These formats can work well for impression-based ads, thanks to their inclination for higher viewability. Simply put, long ads take longer to scroll past. This means that they are more likely to register as viewable.
Refresh for More Value
It’s rare for a user to click on more than one ad in a single page load, as clicking means diverting attention to a new page. Multiple impressions are the norm though, and adding a refresh behavior to ad units can multiply that.
The key to making refresh work is to maintain the value of that inventory. Early refresh systems would keep reloading ads when the placement was out of view, or even on an inactive tab. Such junk inventory is easily detected by advertisers and leads to falling CPMs or even inventory being blocked.
Moderately refreshed units that only reload when in view not only avoid that devaluing of inventory but can bring significant boosts to viewability. Because the incremental impressions are only loaded in-view, these will have close to 100% viewability, bringing the average for the unit up.
Refreshing has even more value when combined with techniques like sticky units that keep the ad in view longer, leading to more refreshes.
Don’t Ignore Clicks
Being paid by impressions doesn’t mean that clicks can be entirely ignored. CTR is still a metric used to indicate inventory quality. Although CPMs ads remove the need to constantly optimize for higher CTR (and risk penalty for “unnatural attention”), units receiving very low CTRs are likely to also have poor performance. There isn’t a particular level to watch for, but being aware of any units that are underperforming vs others on a site can prevent issues from low CTRs.
Making the Switch to CPM
Switching from being paid by the click to being paid by the impression will bring gains for the majority of publishers (there are a few exceptions), but the best results come when you consider who your inventory will perform after the change.
The best approach is usually to switch over inventory on a like-for-like basis, then reassess the performance of each placement in terms of the points above. This allows you, not only to get the most benefit from the change but also to accurately measure the difference.