What is CPM advertising? A plain-English guide

CPM

Cost per mille — the price of a thousand ad views (mille is Latin for thousand). A £2.50 CPM means each thousand times your banner appears costs £2.50. It's the standard way display space is priced, the way print media was before it: you're buying attention, not clicks.

The mental model: CPM buys presence. People rarely click a banner and immediately buy — they see your name on sites they trust, repeatedly, and remember you when they need what you sell. Judge a CPM campaign the way you'd judge sponsoring the village fete, not the way you'd judge a Google search ad.

Viewability

An ad can be "served" without ever appearing on screen — loaded at the bottom of a page nobody scrolls to. A viewable impression means it was genuinely visible: the industry standard is at least 50% of the ad on screen for at least one continuous second. Always ask which one you're being charged for; the gap is around a third of all display advertising. On dijitul ads, only viewable impressions are billed — unseen ads cost nothing.

CTR, and what a good one looks like

Click-through rate: clicks divided by impressions. Display banners typically run 0.1–0.5% — and that's fine, because clicks aren't the main job (see presence, above). Be suspicious of anyone promising banner CTRs of several percent; at that level someone is usually clicking who shouldn't be.

Share of voice

When several advertisers want the same slot, someone decides who appears more often. In our network it's simply proportional to your CPM bid: bid twice the other advertiser and you appear roughly twice as often. No sealed auctions, no algorithmic mystery.

Contextual vs behavioural targeting

Behavioural targeting follows a person around the web based on a profile of them — it's why you see ads for the shoes you already bought, and why every site needs a cookie banner. Contextual targeting matches the ad to the page instead: boiler servicing on a home-improvement blog. No profile, no cookies, no consent banner needed — and for most UK small businesses it's the more sensible buy anyway, because context is intent: someone reading about gardens is a good prospect for a landscaper, whoever they are.

Fill rate

A publisher-side number worth understanding as an advertiser too: the share of a site's ad slots that actually show a paid ad. Networks chasing 100% fill stuff remnant junk into every gap. Slots on our network simply collapse when there's no suitable ad — which is also why your ad never appears beside filler.