Advertising Glossary

The price an advertiser pays for one thousand ad impressions. 'Mille' is Latin for thousand. The dominant pricing model for brand and display advertising, where the goal is to be seen rather than necessarily clicked.

Why it matters: CPM lets you compare the cost of reach across very different placements and formats on a like-for-like basis. It's the baseline currency of programmatic display and the figure most publishers and ad networks quote first.

The amount an advertiser pays each time someone clicks their ad. The advertiser pays nothing for impressions — only for the click that sends a user to their site. The standard model for search and performance campaigns.

Why it matters: CPC ties cost directly to a concrete action, shifting the risk of a poorly-performing ad onto the publisher/platform. It's the natural fit when the goal is traffic or conversions rather than awareness.

The price paid per video view, where a 'view' is defined by the platform — often 30 seconds watched, completion, or an interaction (whichever comes first). Common on YouTube and other video platforms.

Why it matters: CPV aligns spend with actual video engagement rather than mere impressions, so you only pay when someone genuinely watches. Essential for judging the efficiency of video and CTV campaigns.

The cost of acquiring one conversion — a sale, sign-up, or other defined action. The advertiser pays only when the desired outcome happens, making it the most performance-focused pricing model.

Why it matters: CPA maps spend directly to business results, so it's the metric that connects advertising to ROI most cleanly. Marketers compare CPA against the value of a customer to judge whether a campaign is profitable.

A form of CPA specific to lead generation — the cost of acquiring one qualified lead, such as a completed contact form or newsletter sign-up. Common in B2B and high-consideration purchases.

Why it matters: For businesses where the sale happens offline or over a long cycle, the lead is the measurable outcome. CPL lets those advertisers buy media on a results basis even when the final sale can't be tracked directly.

The cost of driving a single app install. The standard pricing model for mobile app-install campaigns, where the tracked outcome is the download and first open of the app.

Why it matters: App marketers live and die by CPI versus the lifetime value of a user. It's the headline efficiency metric for user-acquisition campaigns across app stores and in-app ad networks.

The percentage of impressions that result in a click. It measures how effectively an ad prompts people to act — a direct read on creative and targeting relevance.

Why it matters: CTR is the single most-watched engagement metric in display and search. A low CTR signals weak creative, poor targeting, or banner blindness; a high CTR (in search especially) also improves Quality Score and lowers costs.

The percentage of clicks (or visits) that complete the desired action — a purchase, sign-up, or download. Where CTR measures interest, CVR measures follow-through.

Why it matters: CVR reveals how well the post-click experience — the landing page and offer — turns interest into outcomes. You can have a great CTR and still fail commercially if CVR is poor.

The percentage of video ads played to completion (or to a defined point). VCR measures how many viewers watched all the way through rather than skipping.

Why it matters: For video and CTV, completion is the core engagement signal — it tells you whether your story is holding attention or losing it at the skip button. Strongly tied to brand recall.

The percentage of served ads that were actually viewable — by the IAB standard, at least 50% of the ad's pixels on screen for at least one second (two seconds for video). An ad can be 'served' without ever being seen.

Why it matters: Viewability separates ads that had a chance to make an impression from those that loaded below the fold and were never scrolled into view. It's a quality gate buyers increasingly insist on before paying.

The publisher-side mirror of CPM: the revenue earned per thousand impressions or pageviews. The headline figure in AdSense and other publisher dashboards.

Why it matters: RPM is how a publisher judges how well their inventory monetises. It bundles fill rate, CPM, and ad density into one number you can track and try to improve over time.

A normalised CPM that lets you compare earnings across campaigns sold on different models (CPC, CPA, CPV). It converts whatever was actually earned back into a per-thousand-impressions figure.

Why it matters: Because inventory is sold so many different ways, eCPM is the great equaliser — it answers 'what is this placement really worth per thousand impressions?' regardless of how the deal was priced.

The revenue generated for every unit of currency spent on advertising. Expressed as a ratio or multiple — e.g. a ROAS of 4 means £4 of revenue per £1 spent.

Why it matters: ROAS is the bottom-line measure of whether advertising is paying for itself. It's the metric marketing leaders and finance teams use to judge whether to scale a channel up or cut it.

Reach is the number of unique people who saw an ad; frequency is the average number of times each person saw it. The two are always read together.

Why it matters: Too little frequency and the message doesn't stick; too much and you waste spend and irritate people (ad fatigue). Managing the reach/frequency balance is central to brand campaign planning.

The share of people who actively interact with an ad — clicking, expanding, hovering, swiping, or playing — rather than simply being served it. The exact definition varies by format and platform.

Why it matters: Engagement captures value a click alone misses, especially for rich media and native, where expansions, video plays and swipes signal genuine interest. It's a fuller read on how compelling a creative really is.

How long a user actively spends with an ad — for example, the seconds a cursor rests on an expandable unit, or a rich media experience stays open and in view.

Why it matters: Dwell time is a strong attention signal. Longer engaged time correlates with brand recall and message retention, which is why rich media and high-impact formats track it closely.

Whether people remember seeing an ad afterwards — usually measured as 'ad recall lift', the increase in recall among those exposed versus an unexposed control group, via brand-lift surveys.

Why it matters: For brand campaigns where the goal is memory rather than an immediate click, recall is the outcome that matters. It's how awareness-focused advertisers judge success beyond CTR.

The percentage of delivered emails that are opened. Central to email and newsletter advertising — though increasingly unreliable since Apple's Mail Privacy Protection auto-loads images and inflates opens.

Why it matters: Open rate is the first-stage engagement signal for email placements, reflecting subject-line and sender strength. Because of privacy changes, clicks are now the more trustworthy measure.

The share of users who actively agree to receive messages — granting push-notification permission, subscribing to a newsletter, or consenting to be contacted.

Why it matters: Permission is the foundation of push and email advertising: you can only reach people who opt in, so the opt-in rate caps your addressable audience — and opted-in users are far more engaged than cold ones.

How close a user is to taking action. Searching 'buy running shoes' signals high intent; idly browsing signals low intent. Search advertising targets active intent directly.

Why it matters: Intent is the single biggest driver of conversion rate, and the reason search ads convert so well: you reach people at the exact moment they're looking, rather than interrupting them.

The number of times a person has the chance to see an ad — the standard reach measure for out-of-home and print, where you can't track an actual 'view'. A roadside billboard counts an OTS each time someone passes it.

Why it matters: Where digital can measure real impressions, traditional OOH and print estimate exposure instead. OTS (and its average across an audience) is how those channels are planned, priced and compared.

The automated buying and selling of ad inventory through software and auctions, rather than manual insertion orders and phone calls. It spans open real-time bidding, private marketplaces (PMPs), and programmatic direct deals.

Why it matters: Programmatic is how the vast majority of display is now traded. It lets advertisers buy precise audiences at scale, in real time, across thousands of sites from a single platform — and it's the engine behind most of the formats on this site.

Showing ads to people who have already visited your site or app, identified by a cookie or tracking pixel, to draw them back. The shoes you viewed once and then see everywhere — that's retargeting.

Why it matters: It focuses spend on a warm audience that has already shown interest, so it typically delivers much higher click-through and conversion rates than cold display. Frequency capping matters, though — overdo it and it feels like stalking.

Placing ads based on the content of the page — its keywords, topic, and category — rather than on personal data about the individual viewing it. A running-shoe ad on a marathon-training article is contextual.

Why it matters: Because it needs no personal data, contextual targeting is privacy-friendly and resilient to third-party cookie deprecation — which is driving a major resurgence. Relevance comes from the environment rather than from tracking the user.

Targeting people based on their past online behaviour — pages browsed, searches, purchases, and inferred interests — grouped into audience segments that advertisers can buy.

Why it matters: It enables precise, interest-based reach, but is the form of targeting most affected by privacy regulation (GDPR) and the decline of third-party cookies. The industry is actively shifting toward first-party data and contextual alternatives.

Audiences built algorithmically by finding new users who resemble an advertiser's existing customers or a 'seed' list, based on shared characteristics and behaviour.

Why it matters: Lookalikes let advertisers scale prospecting beyond people they already know while keeping targeting relevant. They're a staple of social platforms (e.g. Meta) and increasingly available programmatically.

The automated auction that decides which ad fills an impression, run in the milliseconds while a page loads. Advertisers bid programmatically on each individual impression based on the user and context.

Why it matters: RTB is the engine of programmatic advertising — it allocates billions of impressions efficiently and lets advertisers buy precisely the audiences they want, one impression at a time.

The software advertisers use to buy ad inventory programmatically across many exchanges and publishers from one interface — setting targeting, budgets, and bids. Examples: DV360, The Trade Desk.

Why it matters: The DSP is the buyer's cockpit. Understanding it explains how a single campaign can run across thousands of sites with unified targeting, bidding, and reporting.

The publisher-side counterpart to a DSP: software publishers use to offer their inventory to many buyers at once and maximise the price each impression fetches. Examples: Google Ad Manager, Magnite.

Why it matters: The SSP is how publishers plug into programmatic demand. Together, DSPs and SSPs meet at the ad exchange to form the programmatic marketplace.

An IAB standard — an XML schema that tells a video player where to fetch a video ad, how long it runs, when a skip button appears, and which tracking events to fire.

Why it matters: VAST is what makes video ads interoperable across players and platforms. Any time you see a pre-roll with a skip countdown, a VAST tag is orchestrating it behind the scenes.

A plain text file a publisher hosts at the root of their domain listing which companies are authorised to sell their ad inventory. An anti-fraud standard from the IAB.

Why it matters: ads.txt combats domain spoofing — buyers can verify that inventory claiming to be from a site is genuinely authorised. It's required for AdSense and most programmatic demand.

The percentage of ad requests that are actually filled with a paying ad. When no advertiser bids high enough (or at all), the slot goes unfilled — lowering fill rate.

Why it matters: Fill rate is a key publisher health metric: unfilled impressions earn nothing. Low fill points to weak demand, overly high price floors, or inventory quality issues.

Television streamed over the internet rather than broadcast or cable — via smart TVs, streaming sticks, games consoles and the ad-supported tiers of streaming services. Ads are bought and measured like digital, but play on the big screen.

Why it matters: CTV is one of the fastest-growing ad channels, bringing TV-scale impact together with digital targeting and measurement. It's where a lot of traditional TV budget is moving.

Advertising sold by a retailer across its own channels — sponsored product listings on its site and app, plus in-store screens — powered by the retailer's first-party purchase data.

Why it matters: Retail media is booming because it sits right at the point of purchase and uses logged-in, real buying data — valuable as third-party cookies fade. Amazon, and increasingly every big retailer, now runs one.

The number of copies of a publication distributed per issue — sold on newsstands, posted to subscribers, and given away. The headline figure for how many copies are out there.

Why it matters: Circulation is the baseline that print ad rates are built on and the main way titles are compared. Audited circulation gives advertisers confidence the figure is real.

The estimated number of people who actually read or look at an issue — usually higher than circulation, because each copy gets passed around (the 'pass-on' rate).

Why it matters: Readership reflects true audience size better than circulation alone: one magazine in a waiting room can be read by dozens. Advertisers ultimately care about eyeballs, not just copies.

The total number of copies printed for an issue, including those that won't be sold. It's the figure the print order is based on.

Why it matters: The print run drives production cost and, set against actual sales, reveals how many copies go unsold. Print run minus returns is a real read on demand.

Unsold copies sent back from retailers (or pulped). The return rate is returns as a share of the copies distributed.

Why it matters: Returns show how accurately a title is printed to demand — a high rate means wasted print and distribution. 'Net' circulation counts sales after returns.

Copies sold on a standing order — delivered regularly to a reader who has signed up — as opposed to single copies bought at the newsstand.

Why it matters: Subscribers are a committed, predictable, well-profiled audience advertisers value. A healthy subscription base also smooths revenue and cuts returns.

Copies supplied free or deeply discounted in bulk to places like hotels, airlines, gyms and events, where they're read by many people.

Why it matters: Bulks lift circulation and reach, but advertisers scrutinise them — a copy left in an airport lounge isn't the same as one a subscriber chose to buy. Audited figures break them out separately.

An independent industry body that verifies and publishes the circulation figures publishers report, so the numbers advertisers buy against can be trusted.

Why it matters: ABC-audited figures are the gold standard for print media buying — they stop publishers marking their own homework and give advertisers a like-for-like basis to compare titles.

A publisher's published list of standard prices for its ad spaces — by size, position and any premiums. The starting point for a media negotiation.

Why it matters: The rate card is the reference price; real deals are often agreed below it. Knowing it lets advertisers judge value and compare titles on a common footing.

The cost to reach one thousand readers (or copies) — print's equivalent of digital's CPM ('mille' is Latin for thousand). It normalises price so different titles can be compared.

Why it matters: CPT is the great equaliser in print planning: a cheap full page in a small magazine can be worse value than a pricier one in a bigger title once audience is accounted for.

Artwork extended beyond the page's trim edge so that, once the page is cut, the design runs right to the edge with no white border. Standard bleed is a few millimetres.

Why it matters: Without bleed, a slightly off cut leaves a thin white strip at the edge. Full-bleed ads must be supplied with bleed — a basic but commonly-missed print spec.

The inner margin where two facing pages meet at the binding. On a spread, content placed in the gutter can disappear into the fold.

Why it matters: It's why double-page-spread ads keep key elements — logos, faces, text — clear of the centre: anything in the gutter risks being swallowed by the binding.

A single appearance of an ad in one issue of a publication. Booking the same ad in three issues is three insertions.

Why it matters: Print buys and discounts are counted in insertions — a 'series discount' rewards booking several. It's the basic unit of a print schedule.

The standard way newspaper ad space is priced — by the centimetre. An ad's cost is its height in centimetres × the number of columns it spans × the rate per single column centimetre. A 20cm-tall ad across 3 columns is 60 SCC.

Why it matters: SCC pricing lets newspapers sell flexible, irregular ad shapes by area rather than fixed slots — which is exactly why display and classified ads in papers come in so many sizes.

How magazines and many weeklies price ads — as fixed 'modules' (full page, half page, quarter page, DPS), each at a set flat rate, rather than by the centimetre. You buy a standard unit, not an area.

Why it matters: Modular pricing keeps magazine layouts clean and rate cards simple — a handful of standard sizes at known prices, instead of the newspaper's more granular column-centimetre maths.