This glossary defines 81 terms in plain English.

The number of distinct people or households exposed to a campaign at least once, as opposed to the total number of impressions delivered. Usually expressed as a count or as a percentage of a defined universe.

In practice: Reach across channels is almost always modelled, because no single seller can see the others, and no UK service de-duplicates reach across out-of-home, streaming TV, podcasts and ChatGPT ads. AdBuyMCP's weekly report keeps each channel's count in its own unit, and any reach AdBuyMCP models carries the label modelled wherever it appears. Adding each channel's reach together inflates the total, because a household reached on two channels is counted twice.

A brand's advertising presence expressed as a proportion of all advertising in its category, in a given market and period. Used as a planning benchmark on the argument that share of voice above share of market tends to precede growth.

In practice: Useful for setting a budget's order of magnitude and of little use for judging a campaign, because it is a share of spend. It is worth knowing mainly because it is the reasoning behind most large brand budgets, and therefore the frame a buyer arrives with when they ask what a channel costs. An AdBuyMCP awareness plan is sized another way, from the number of people in your market and how often they should see you.

All advertising encountered outside the home: billboards, transport, street furniture and retail environments, printed or digital. Covers both classic printed sites and the digital screens that are steadily replacing them.

In practice: Worth separating from DOOH when reading a media plan, because the two behave differently. Classic OOH is bought for a fixed period at a fixed price and cannot be paced, targeted by daypart or turned off, while digital screens can. Outsmart put UK out-of-home revenue for 2025 at £1.44bn, 67% of it digital (checked 20 October 2026), so an out-of-home line in a plan is usually partly digital. An AdBuyMCP awareness plan can book both: printed sites by place, and digital screens by place and time of day.

Software a publisher uses to sell its advertising inventory to many buyers at once, running the auction and setting price floors. It sits on the seller's side of the same market a DSP buys from.

In practice: An SSP matters to a buyer because of the fee stack: a supply-side platform takes a fee and an exchange layer can take another on top of it, which is how the cumulative 'ad tech tax' arises without any single layer looking expensive. Knowing the SSP layer exists is what lets you ask the question that settles a media price: how much of this pound reaches the publisher?

A marketplace in which advertising impressions are auctioned between demand-side platforms buying and supply-side platforms selling. It matches bids to inventory in the milliseconds between a page or stream starting to load and the advert appearing.

In practice: Mostly invisible to a buyer, and mostly should be, except that each hop in the chain takes a margin, and the number of hops is rarely disclosed. Supply-path transparency, meaning a published account of which intermediaries a bid passes through, is something the largest advertisers now demand and smaller ones almost never get.

The auction mechanism underneath most programmatic advertising: when an impression becomes available, buyers bid on it and the winner's advert is served, all within roughly a hundred milliseconds.

In practice: For a buyer, price is set per impression rather than per campaign, so a plan's CPM is a forecast. The auction is also where most of the ad tech fee stack is levied, which is why the cumulative take between advertiser and publisher can be far larger than any single platform's disclosed rate.

A negotiated arrangement in which a publisher makes specific inventory available to specific buyers at agreed terms, transacted programmatically through a deal identifier rather than in the open auction.

In practice: This is how named-show podcast buying and most premium audio actually happens: you negotiate a deal, then execute it programmatically. AdBuyMCP's audio compiler emits a named-show package as a deal specification, because the deal has to exist before the plan can spend against it.

The identifier that carries a negotiated private-marketplace arrangement into a programmatic buying system at auction time, telling the auction which buyer gets access to which inventory at which agreed price.

In practice: Worth knowing because it is the practical boundary between what a platform can buy on your behalf today and what needs a conversation first. AdBuyMCP's compiled channel plans start with no deals attached: a deal is added when a buyer hand-picks inventory or when one has been negotiated.

The cost of one click on an advert, and the standard price unit for paid search and for much of paid social, where the advertiser pays for a response rather than for the impression that produced it.

In practice: A CPC transfers delivery risk to the seller, which is why it dominates the channels where clicks are plentiful and is almost unknown on television, cinema and out-of-home. Comparing a CPC channel to a CPM channel on cost per click is a category error: it flatters search and tells you nothing about whether the other channels created the demand search then harvested.

The cost of one completed action, whether that is a sale, a lead or a booking, calculated by dividing spend by the actions attributed to it. That makes it entirely dependent on the attribution model underneath.

In practice: CPA is widely quoted, but two CPAs are only comparable if they share an attribution window, a model and a definition of the action, and they almost never do. A CPA computed on last-click will always flatter search and starve everything that created the demand. This is the number an incrementality test exists to check.

A pricing model in which the advertiser pays only when a defined outcome occurs (an install, a purchase, a store visit), with the platform carrying the delivery risk and embedding its margin in the outcome price.

In practice: The most aggressive pricing innovation in this category. tvScientific offers it on connected TV, restricted to qualifying advertisers. For a performance buyer who qualifies, it can be the better offer. It requires measurement maturity and risk capital, and AdBuyMCP does not offer it: its awareness plans are priced on the size of your market and how often it should see you.

The portion of an advertising budget that actually buys advertising, as opposed to the portion consumed by platform fees, data costs, agency fees, ad serving and production. Usually expressed as a percentage of total spend.

In practice: Working media is the number to compare fees on. A platform fee on top of a data cost and an agency retainer adds up to more than any one of them, and every intermediary between the advertiser and the publisher takes its share before the money arrives: ISBA's 2020 study with PwC found about half of advertiser spend reaching publishers. Under an all-in price, such as an AdBuyMCP plan's, the working-media share sits inside the price, so the useful question becomes what each channel delivered against the plan.

The cumulative share of an advertiser's budget taken by the intermediaries between advertiser and publisher, none of which individually looks large. Those are the demand platform, exchange, supply platform, data vendors and verification.

In practice: It is cumulative and mostly undisclosed, which is why it is the category's most persistent grievance. The defence is supply-path transparency: knowing which intermediaries a bid passes through and what each one keeps.

A seller's published list prices for its advertising inventory, before any negotiation, discount or volume agreement is applied to them. In practice most large media is bought below rate card, which makes the card a starting position rather than a price.

In practice: Relevant to a small advertiser mainly as a warning: the discount available depends on the volume behind them, which is one of the genuine arguments for buying through an intermediary. It is also the reason a published platform fee and a published rate card are different kinds of promise.

Audience data collected by one organisation and licensed to another for targeting, with no direct relationship between the licensee and the people described. Sold as segments through data marketplaces attached to buying platforms.

In practice: Third-party data can add its own cost on top of the media, so ask whether a quote includes the audience. You also need to know where it came from, which is what a lawful-basis manifest exists to answer: which provider, on what basis, with which conditions still owed by you. Consent-chained means the provider asserts a consent chain. Nobody downstream has necessarily verified every link in it.

Targeting based on the content an advert appears beside rather than on data about the person seeing it: a show, a genre, a page subject, a venue type. Requires no personal data about the audience.

In practice: Because it needs no personal data, contextual targeting is increasingly the sensible default as behavioural identifiers decline. It is how an AdBuyMCP awareness plan buys podcasts, by show and category, and ChatGPT ads, matched to the topic of a conversation; AdBuyMCP's audio compiler expresses it as show and genre allowlists, graded content-level at 65. The same logic puts cinema and DOOH delivery outside UK GDPR scope: a venue catchment is a property of a place.

An audience built by finding people who resemble a seed group (usually the advertiser's existing customers) on whatever signals the platform holds. The resemblance model is the platform's and is not disclosed.

In practice: Effective and opaque in equal measure, and available only where a platform has both your seed list and enough signal to model against it, which in practice means the large social platforms. A lookalike inherits every bias in the seed: modelling on your existing customers reliably finds more people like your existing customers, and growth usually needs someone new.

Showing advertising to people who have already interacted with a brand: visited a site, abandoned a basket, opened an email. Depends on being able to recognise the same person again on a later occasion.

In practice: The channel where attribution flatters itself most, because retargeting reaches people who were already going to convert. It usually looks like the best-performing line in a plan and is usually the one most in need of an incrementality test. A geo-lift or holdout design is the reliable way to find out how much of it was incremental.

Removing the double-counting that occurs when the same person is reached by more than one channel or placement in a campaign, so that combined reach reflects distinct people rather than the sum of each channel's separate count.

In practice: The reason a cross-channel plan needs one exposure record where it would otherwise have a report from every seller. Without it, a launch that buys the same households on television, streaming and out-of-home reports three audiences that are substantially one audience, and the number that reaches a board is wrong by a wide and unknowable margin. Deduplication at launch matters more than at any other moment, because a launch buys the same people repeatedly by design.

A UK geodemographic classification that assigns every household to one of a set of named types based on demography, affluence, life stage and location. Used to select households for addressable television and direct media.

In practice: UK addressable television is bought in Mosaic's vocabulary. A brief naming senior business decision makers compiles into Mosaic groups and occupation attributes intersected with postcode districts, which is why the grade is household, and why AdBuyMCP's catalogue grades addressable TV 55 out of 100. You are buying homes whose profile over-indexes on the attribute you asked for.

A UK consumer classification that segments postcodes into named types by demographics, lifestyle and behaviour, used to rank areas rather than people. In practice that means catchment work: which cinema, which retail park, which high street.

In practice: The intended basis for ranking cinema venues by how far their catchment over-indexes on a target audience. We do not hold an Acorn licence. Cinema venue lists are currently built from the persona's own postcode districts, the catchment over-index figures shown on a sandbox booking brief are sample data, and the client for CACI's postcode classification API is built but holds no licence and no Acorn data. The supply page grades it accordingly.

A consent-based identifier for European advertising, derived from a hashed email or phone number provided with consent, designed to let first-party audiences be addressed across publishers without third-party cookies.

In practice: The intended bridge from a customer list to premium inventory under UK and EU data protection. AdBuyMCP's CTV compiler emits an empty EUID audience list, so no plan carries one today: the EUID client is built and waits on an EUID participation agreement.

An open-source, consent-based advertising identifier derived from a hashed email or phone number, developed as an industry alternative to third-party cookies. EUID is its European counterpart.

In practice: Mentioned here mainly so the family is legible: UID2 is the North American implementation and EUID the European one, and a vendor discussing one may mean either. Neither is in use here today.

A dataset linking devices, identifiers and addresses believed to belong to the same household, allowing a television, a laptop and a phone in one home to be recognised as one buying unit.

In practice: What makes deduplication between connected TV and addressable television possible at all, since neither can see an individual. It is also the point where a privacy review should press hardest, because a household graph is an inference about people who never supplied it. AdBuyMCP's ledger keys on an opaque household key issued by a separate key-translation service and never resolves it back to anything.

The process of deciding that two different identifiers refer to the same person or household, so that behaviour seen under one can be joined to the other.

In practice: The highest-risk operation in advertising data and the one worth isolating architecturally. In AdBuyMCP exactly one module performs identity joins (the key-translation service), and the exposure ledger every channel writes into never resolves a key back to a person or across key spaces. That boundary is why the 90-day retention rule has one place to be enforced and one place to be audited.

A standardised, encoded record of what a user consented to, produced at the point of collection and readable by every participant downstream. It is passed along the advertising supply chain so that each participant can check whether it has a basis to process that person's data before it does.

In practice: The consent string is what lets a buyer check a 'consent-chained' claim. AdBuyMCP's policy engine attaches a standing condition to every consent-chained data source requiring that the supply chain be framework-validated and that the vendor attestation be verified on connection. That is a condition you still owe, and a lawful-basis manifest is a list of conditions of that kind.

A control market chosen because its historical outcome pattern closely tracks the test market's, so that a later divergence can be attributed to the campaign.

In practice: Matching is done on the pre-campaign series, because two cities that look alike on paper often behave differently commercially. Getting this wrong is invisible in the output: a badly matched pair produces a confident number that means nothing, which is why the pairing and the power analysis both have to happen before the media runs.

A method that compares the change in an exposed group against the change in a control group over the same period, so that anything moving both in step (seasonality, a competitor, the weather) cancels out.

In practice: The readout underneath a geo-lift result. It is worth understanding because it explains what the test is actually robust to: shared shocks cancel, and anything that hit only the test markets stays in. That is the residual risk in any geo experiment and the reason a result should carry a confidence interval as well as a point estimate.

An attribution rule that gives all the credit for an outcome to the final advertising touchpoint before it, and none to the rest. Simple, universally available, and systematically biased towards whichever channel sits closest to the conversion.

In practice: It reliably over-credits search and retargeting and under-credits everything that created the demand they harvested, which is why a business optimising purely on last-click tends to shrink towards its existing customers. It is still useful as a consistent operational signal, but it cannot answer whether a channel was incremental, and no amount of modelling on top of it turns it into an answer.

Whether an advert was actually rendered in a position where a person could have seen it, measured against an industry threshold: commonly half the pixels for one second for display, two seconds for video.

In practice: A served impression and a viewable impression are different things, and the gap is where a meaningful share of digital budgets goes. AdBuyMCP has no independent verification integration yet: no viewability, brand-safety or fraud vendor is wired in.

A seller-supplied record confirming that a specific advert played on a specific screen at a specific time, with the play logged rather than estimated. The out-of-home equivalent of an impression log, since a screen cannot report who was in front of it.

In practice: The strongest delivery evidence out-of-home can produce, and the reason a DOOH report proves the media ran. It is a delivery fact about the screen, and a plan that treats proof-of-play counts as reach is overstating by whatever the seller's audience model says.

The industry XML standard that tells a video player where to fetch an advert, how long it runs and which tracking events to fire. Most connected TV and online video advertising runs on VAST.

In practice: Relevant to a buyer mainly as a delivery requirement: a CTV creative is a video file plus its trafficking metadata, and a mismatch between them is a common reason a campaign fails to start. AdBuyMCP generates storyboards with the metadata attached so the creative and its trafficking record are one object.

A label attached to a number recording how it was produced, so anyone reading the number can see how strong the evidence behind it is. The number may be reported by the seller, observed on your own property, estimated by a model, or established by a powered experiment.

In practice: The mechanism that keeps four kinds of evidence from collapsing into one flattering number. AdBuyMCP uses four labels: provider-reported, observed, modelled and powered causal, and only the last supports the word caused. The governing rule is blunt: no provenance label may advance on the strength of sandbox or API-shaped data. That is why no sandbox campaign can ever reach a causal grade, and none has.

A number produced by a formula or an estimate rather than counted directly from observed events, and therefore carrying assumptions with it. Deduplicated reach and frequency across channels are the common examples, since no single seller can observe the others.

In practice: The word matters because a modelled number and a counted one look identical in a report. AdBuyMCP's reach and frequency figures carry the label modelled wherever they appear, so a modelled estimate cannot be quoted as an observation by accident.

A lawful basis permitting processing necessary for interests pursued by the controller or a third party, provided those interests are not overridden by the rights of the individual. Requires a documented balancing assessment.

In practice: The basis most advertising targeting actually relies on, and the one most often asserted without the assessment that makes it valid. AdBuyMCP attaches a standing condition to every legitimate-interest source stating that an assessment must be on file for it. That condition states what you owe; it does not confirm the assessment exists.

A freely given, specific, informed and unambiguous indication that someone agrees to their data being processed. Must be as easy to withdraw as to give, and cannot be inferred from silence or inactivity.

In practice: In advertising, consent is usually collected far upstream by a publisher or a data vendor and passed down the chain as an encoded string. 'Consent-chained' means a provider asserts that chain exists. Nobody downstream has necessarily verified every link in it. Withdrawal propagation, meaning that a withdrawal upstream actually stops downstream processing, is the part most implementations handle worst.

The documented three-part test of purpose, necessity and balancing that underpins any reliance on legitimate interests. It must be completed and retained before an organisation may rely on legitimate interests as its lawful basis for processing personal data.

In practice: The document a data protection officer will ask for first when a plan relies on legitimate interests, and the one most advertisers discover they do not have. AdBuyMCP surfaces the requirement as a condition on the compiled plan, so it arrives before the review does, and producing the assessment is the advertiser's obligation.

A structured assessment of the privacy risks of a processing activity, required where processing is likely to result in a high risk to individuals, as large-scale profiling for advertising generally is.

In practice: AdBuyMCP has not completed an impact assessment for its exposure ledger. The inputs one would draw on (per-source lawful basis, per-key legal grading and a documented retention rule) exist, and the assessment itself does not.

The body that clears advertising for UK cinema, issuing a certificate and an age rating that determines which films an advert may be shown alongside. Separate from broadcast clearance and required before print traffic.

In practice: The age rating is a media constraint as much as a creative one: copy containing strong language restricts pairing to 15 and 18 certificate films, which changes the audience you can reach. That is worth knowing at the scripting stage, before production, which is why the pre-check flags it there.

The two UK advertising codes, enforced by the Advertising Standards Authority: BCAP governs broadcast advertising and CAP governs everything non-broadcast. They set the rules on substantiation, harm, offence and specific product categories.

In practice: Under both codes, objective and superlative claims need documentary substantiation. Medicines, medical devices and health claims require evidence and are frequently blocked outright. Rules on specific categories (alcohol, gambling, financial products) constrain both copy and placement. AdBuyMCP's pre-check names the rule alongside each finding, so a flag tells you what to fix.