Digital advertising 101: display, video, CTV, retail media and programmatic

Digital advertising, in this primer, means paid adverts placed on other companies' websites, apps and streaming services: display (banners and native units), online video, connected TV (CTV, streaming on a television set) and retail media (retail media, adverts sold by retailers on their own sites, apps and data). Search and social advertising have their own primers. As of October 2026, IAB and PwC put US internet advertising revenue at a record $294.6 billion in 2025, up 13.9% on 2024, with digital video up 25.4% to $74 billion¹.

In one line: digital advertising sells one impression at a time, to a buyer who can choose the audience, the context and the price, and who can see, at least in part, what happened next.

Most display, video and CTV inventory is bought programmatically (programmatic): software buys an impression, one at a time, as a page, app or stream loads. Two kinds of platform meet in the middle. The publisher uses a supply-side platform (SSP) to offer its space; the advertiser or agency uses a demand-side platform (DSP) to decide which impressions to buy and at what price.

Three standards keep the chain honest. With ads.txt, a publisher lists on its own site the companies authorised to sell its inventory; version 1.1 in 2022 added fields naming the owner and the manager of the inventory¹³. With sellers.json, each SSP or exchange publishes who sells through it, so buyers can check whether each seller is a direct seller or an intermediary¹². And viewability sets a minimum for an impression to count as seen: under the Media Rating Council's guidelines, at least 50% of an ad's pixels in view for one continuous second for display and two continuous seconds for video¹¹.

Targeting draws on three kinds of data: the context (the page or programme), first-party data (what a publisher, retailer or advertiser knows about its own customers, with their consent) and, where allowed, identifiers such as cookies and mobile advertising IDs. Retargeting shows ads to people who visited a site before; it depends on those identifiers.

Connected TV and retail media

CTV is sold by streaming services and TV makers. It looks like television to the viewer, a full-screen advert on the living-room set, but it is bought and counted like digital: per impression, often through a DSP, with the streamer's own data used for targeting. Retail media is sold by retailers. A retailer's search results, product pages and apps carry adverts, and the retailer can offer its shopper data to target them both on and off its own site; because the sale happens on the same platform, the retailer can report on purchases as well as clicks.

Who does what

• The advertiser sets the objective, audience and budget, and owns its first-party data.
• The agency or in-house team plans, runs the DSP, sets bids and reads the reports.
• The publisher or retailer owns the space and the audience, sells through an SSP or its own platform, and keeps ads.txt up to date¹³.
• Verification and measurement companies check brand safety, fraud and viewability against the MRC's guidelines¹¹.

HotWired, the web offshoot of Wired, began selling banner advertisements in October 1994; AT&T's is the one usually remembered as the first⁵. Programmatic buying and real-time auctions grew through the following decades, and with them a longer and less visible chain between buyer and publisher.

By 2020 that chain had become a problem advertisers could measure. A study by ISBA, the UK advertisers' association, and PwC found that only 51% of programmatic spend reached publishers and that 15% could not be attributed at all, the "unknown delta"¹⁴¹⁵. The industry answered with transparency standards: IAB Tech Lab released sellers.json in 2019¹² and an updated ads.txt in 2022¹³. Privacy changed the rules at the same time: Apple required apps to ask before tracking from iOS 14.5 in 2021⁹¹⁰, the EU adopted the Digital Services Act in 2022¹⁶, and Google, which began restricting third-party cookies for 1% of Chrome users in January 2024 as a test⁶, said in April 2025 that it would keep its current approach to cookie choice rather than introduce a new prompt⁷, then retired most of its Privacy Sandbox technologies in October 2025, citing low adoption⁸.

Digital advertising is used everywhere businesses advertise, and it is the part of the market that grows fastest. WPP Media forecasts total global advertising revenue of about $1.3 trillion in 2026, up 8.9%²; digital channels take most of that growth.

• Americas. The US market reached $294.6 billion in 2025, by IAB and PwC's count¹.
• Europe. The market works under the strictest privacy and platform rules, from consent for cookies to the Digital Services Act¹⁶¹⁷.
• Middle East and Africa. Online advertising falls under media law: the UAE's federal media law covers digital content, and Saudi Arabia's media regulator GCAM has required advertising licences for online advertising by non-Saudi residents²⁰²¹.
• Asia-Pacific and worldwide. Retail media is the newest large format: WARC expects it to pass $200 billion worldwide in 2026³, though its growth is slowing⁴.

Digital advertising spans the whole funnel. Video and CTV serve brand awareness and product launches. Display, retargeting and retail media serve customer acquisition, conversion and lead generation. Retail media is used most by brands sold through big retailers, in consumer goods and retail and e-commerce; B2B software firms lean on display and retargeting to reach buying committees.

In an integrated plan it is often where the other disciplines' work is picked up and converted. Its results look precise, but clicks and last-touch attribution overstate what advertising caused; incrementality tests and the methods in measuring effectiveness show what it really added. The discipline's hub is digital advertising.

Digital media is priced by what the buyer is willing to pay for an outcome or an exposure:

• Per thousand impressions (CPM), the default for display, video and CTV, often on viewable impressions only¹¹.
• Per click (CPC) or per action (CPA), where the platform takes the risk of performance.
• Per completed view for some video formats.
• Fixed-price direct deals for premium inventory, such as a streaming service's sponsorships.

In the open auction, prices are set bid by bid, so there is no rate card to quote; platforms publish their fee rules, not market prices. What matters as much as the media price is how much of each dollar reaches the publisher. In the 2020 ISBA and PwC study, 51% of spend reached publishers and 15% was the unknown delta; the remaining 34%, by subtraction, went to identified costs along the chain¹⁴. In the follow-up study published in January 2023, the share reaching publishers rose to 65% and the unknown delta fell to 3%¹⁴.

This section describes the main frameworks; it is not legal advice.

• European Union. Under the Digital Services Act, online platforms must label adverts, say on whose behalf they run and who paid, and give the main targeting parameters; they may not show adverts based on profiling with special categories of personal data, nor profiling-based adverts to users they know to be minors; and very large platforms must keep public ad repositories¹⁶.
• Cookies and consent. In France, the CNIL requires consent before most cookies and trackers are read or written, under the national transposition of the ePrivacy Directive; refusing must be as easy as accepting, and simply continuing to browse is not consent¹⁷.
• United States. The FTC's substantiation policy applies online as on air: objective claims need a reasonable basis before the advert runs¹⁸.
• United Kingdom. Online adverts follow the non-broadcast CAP Code, enforced by the ASA¹⁹.
• The Gulf. The UAE's media law covers advertising in digital media, and a media licence may be needed²¹; in Saudi Arabia, GCAM has barred non-Saudi residents from posting advertising content online without an advertising licence²⁰.
• Platforms. Apple requires apps to ask permission before tracking people across other companies' apps and websites, and people keep the app's full capabilities whichever they choose⁹; since 26 April 2021, without permission the device's advertising identifier reads as all zeros¹⁰.

• Viewable is not viewed. The MRC threshold is an opportunity to see, not proof of attention¹¹.
• Money leaks. Without checks on ads.txt and sellers.json, buyers can pay for inventory from unauthorised resellers¹²¹³; the ISBA studies show how much can disappear¹⁴.
• Signals are thinning. Apple's tracking prompt and consent rules reduce the identifiers that targeting and measurement rely on⁹¹⁷.
• Precise-looking metrics flatter. Clicks and last-touch attribution credit ads with sales that would have happened anyway; test for incrementality.
• Cookie plans changed. Teams that rebuilt their stack for Privacy Sandbox saw Google retire most of it in 2025 for low adoption⁸.
• Profiling limits. In the EU, profiling-based ads to known minors and ads built on sensitive data are banned on platforms¹⁶.

• Retail media keeps growing, more slowly. WARC expects retail media to pass $200 billion in 2026³, with growth slowing⁴.
• Cookies stay in Chrome; tracking stays limited. Google kept its current approach to third-party cookies and retired most Privacy Sandbox technologies⁷⁸, while consent rules and Apple's prompt still apply⁹¹⁷.
• More enforcement of transparency. The DSA's ad repositories and profiling limits are in force for platforms in the EU¹⁶.
• Video keeps gaining. US digital video grew 25.4% in 2025, faster than the market as a whole¹.

Choose it when you need to reach a defined audience at any budget, change course quickly and connect advertising to sales. Pair it with search and social, and use which mix for which objective to weigh it against the other disciplines.