Programmatic Advertising Wiki

Adscripto Wiki

Programmatic Advertising: A Complete Primer

How the online advertising ecosystem works — from the publisher's sell side to the advertiser's buy side, and every deal type, protocol and platform that connects them.

Contents

1. The two sides of online advertising
2. The ecosystem & who's who
3. Sell side (publishers)
4. Deal types: Direct, PG, PD, PMP, Open
5. RTB & OpenRTB (oRTB)
6. Ad formats
7. Buy side (advertisers)
8. Channels: search, social, programmatic
9. Targeting & retargeting
10. Platforms & the tech stack
11. How an ad auction works
12. Glossary of acronyms

01. The two sides of online advertising

Every digital ad transaction has a seller and a buyer. Understanding the two “sides” is the foundation for everything else.

Online advertising is a marketplace. On one side, publishers (websites, apps, streaming services) have audiences and ad space to sell. On the other, advertisers (brands and their agencies) want to reach those audiences. The systems that connect the two — matching the right ad to the right person at the right moment, often in the ~100 milliseconds a page takes to load — are what we call ad technology, or AdTech.

Supply

Sell side

Publishers and app developers who own the audience and the inventory (the ad slots). Their goal: maximise revenue per impression while protecting user experience. Their core tools are the ad server and the SSP.

Demand

Buy side

Advertisers, brands and agencies who want to reach specific audiences to drive awareness, consideration or sales. Their goal: reach the right people efficiently. Their core tool is the DSP.

Sitting in the middle are the ad exchanges — the marketplaces where supply and demand meet in real time — along with data and measurement layers. The rest of this primer walks through each side in turn.

02. The ecosystem & who's who

The key players that route an ad from advertiser to audience.

Buy side Exchange Sell side Audience Support layers

The programmatic pipeline end to end — how a single impression travels from advertiser to audience.

Player	Side	What it does
Ad Server	Both	Stores, serves and tracks ad creatives. Publishers use one (e.g. Google Ad Manager) to manage inventory; advertisers use one to host and measure creatives.
SSP	Sell	Supply-Side Platform. Lets publishers connect their inventory to many demand sources and auction each impression for the best price.
DSP	Buy	Demand-Side Platform. Lets advertisers buy impressions programmatically across many exchanges from a single interface, with targeting and budget controls.
Ad Exchange	Middle	The digital marketplace where SSPs and DSPs transact impressions in real time via auctions.
DMP / CDP	Both	Data platforms that collect and organise audience data used for targeting and measurement.
Ad Network	Middle	Aggregates inventory from many publishers and resells it to advertisers — the pre-programmatic model, still used in some channels.

---

03. Sell side — the publisher's world

How publishers package and sell their ad inventory.

A publisher's inventory is finite: a fixed number of impressions across their pages and apps each day. The art of the sell side is filling that inventory at the highest possible yield. Publishers do this through a spectrum of deal types — from hand-negotiated direct sales at one end to fully open, automated auctions at the other. Every impression is ultimately managed and measured through the publisher's ad server, and monetised through one or more SSPs.

Yield management is the sell-side discipline of deciding, impression by impression, which demand source — a direct deal, a private deal or the open auction — will pay the most, and routing the impression there. Header bidding and unified auctions were built to make this competition fairer and more transparent.

04. Deal types: Direct, PG, PD, PMP & Open Auction

Programmatic deals differ on two axes: is the inventory reserved/guaranteed, and is the price fixed or set by auction?

Direct-sold DIRECT / IO

The traditional model. A publisher's sales team negotiates directly with an advertiser and signs an Insertion Order (IO) — a contract for a set number of impressions at a fixed price. Reserved and guaranteed, but manual and slow. Programmatic deal types were created to bring this same certainty into automated pipes.

Programmatic Guaranteed PG

The automated version of a direct deal. One advertiser reserves a guaranteed volume of specific inventory at a fixed CPM — no auction, no competition. It combines the certainty of a direct buy with the efficiency of programmatic pipes (automated trafficking, unified reporting). Best for premium, high-confidence placements.

Preferred Deals PD

A one-to-one deal at a fixed, negotiated price, but non-guaranteed — the buyer gets a “first look” at the inventory before it goes to auction, but is under no obligation to buy, and the publisher isn't obliged to reserve volume. Useful when a buyer wants priority access without committing to a fixed spend.

Private Marketplace PMP

An invitation-only auction. The publisher invites a select group of buyers to bid on premium inventory via a Deal ID, usually with a price floor. It offers more control and transparency than the open market while retaining auction dynamics. “PMP” is often used as the umbrella term for private, invitation-based programmatic — encompassing both Private Auctions (multiple invited buyers competing) and Preferred Deals (a single buyer, fixed price).

Open Auction RTB / OPEN EXCHANGE

The fully open marketplace. Any buyer connected to the exchange can bid on the impression in a real-time auction, with the highest bid (above the floor) winning. Maximum reach and liquidity, lowest control — this is where the bulk of remnant inventory clears. Powered by RTB (see next section).

The classic quadrant. Google popularised describing programmatic deals across two dimensions — reservation and pricing:

	Fixed price	Auction price
Reserved / guaranteed	Programmatic Guaranteed1 buyer, guaranteed volume	(rare)
Unreserved / non-guaranteed	Preferred Deals1 buyer, first look	Private Auction & Open Auctionmany buyers, floor price

Certainty ↓ as you move down & right Reach ↑ as you move down & right Deal ID links buyer & deal terms

05. RTB & OpenRTB (oRTB)

The real-time plumbing behind auction-based buying.

Real-Time Bidding (RTB) is the mechanism that auctions a single impression in the moment it's being created — as a page or app loads. When a user arrives, the SSP sends a bid request describing the impression (site, format, device, geo, available audience signals) to connected exchanges and DSPs. Each DSP evaluates it against its advertisers' campaigns and returns a bid response with a price and a creative. The highest eligible bid wins and its ad is served — all within roughly 100–300 milliseconds.

OpenRTB (oRTB) is the standard protocol that makes this possible. Maintained by the IAB Tech Lab, it defines a common JSON specification for bid requests and responses so that any SSP can talk to any DSP without custom integrations. It is the lingua franca of programmatic; features like Deal IDs (for PMP/PG), supply chain object (sellers.json / SupplyChain, for transparency) and first-party identifiers all ride on top of the oRTB spec.

Header bidding is a sell-side technique where publishers offer inventory to multiple exchanges simultaneously (via code in the page header, e.g. Prebid) before calling their ad server — replacing the old sequential “waterfall” and letting demand sources compete on a level field for higher yield.

06. Ad formats

The creative shapes that fill inventory across screens.

Format	Description
Display / Banner	Static or animated image ads in standard IAB sizes — 300×250 (medium rectangle), 728×90 (leaderboard), 160×600 (skyscraper), 320×50 (mobile banner), 300×600 (half-page), 970×250 (billboard).
Native	Ads styled to match the look and feel of the surrounding content (in-feed units, recommendation widgets). Less disruptive, higher engagement.
Video	Instream (pre-, mid-, post-roll inside video content) and outstream (video that plays within an article). Delivered via the VAST standard; interactivity historically via VPAID, now superseded by OMID / SIMID.
Rich media	Interactive, expandable or overlay units with video, animation and user interaction.
Audio	Ads served inside streaming music and podcasts, with companion display units.
CTV / OTT	Ads on connected TVs and over-the-top streaming apps — the fastest-growing premium video channel.
DOOH	Digital Out-of-Home — programmatic buying of digital billboards and screens in physical spaces.
Interstitial / Rewarded	Full-screen units (interstitial) and opt-in ads that reward users with in-app value (rewarded), common in mobile apps and games.

---

07. Buy side — the advertiser's world

How brands reach audiences across digital channels.

Digital marketing is the practice of promoting products and services through digital channels. Advertisers work down a funnel — building awareness at the top, driving consideration in the middle, and converting to action (a sale, sign-up or lead) at the bottom — and they choose channels and tactics to match each stage. The buy side spans several overlapping approaches: search, social, and programmatic display/video, all increasingly powered by audience data.

08. Channels: search, social & programmatic

Search advertising SEM / PPC

Text and shopping ads shown against search queries (e.g. Google Ads, Microsoft Advertising). Bought on a cost-per-click (CPC) basis via keyword auctions. High intent — the user is actively searching — so it's a workhorse for bottom-funnel performance.

Social media advertising

Ads bought inside walled-garden platforms — Meta (Facebook, Instagram), LinkedIn, TikTok, X, Snap, Pinterest, YouTube. Each has its own self-serve ad manager and rich first-party audience data, enabling precise interest, demographic and behavioural targeting. Strong across the full funnel, especially for brand building and lookalike prospecting.

Programmatic advertising

The automated buying of ad inventory (display, video, CTV, audio, DOOH) across the open web and apps through a DSP, transacting with publishers' SSPs via the deal types and RTB described on the sell side. It lets a single campaign reach audiences across thousands of sites and apps with unified targeting, frequency capping and measurement — the scaled, data-driven complement to search and social.

09. Targeting & retargeting

How advertisers decide who sees an ad.

Approach	How it works
Contextual	Targets the content of the page (a running-shoe ad on a marathon article), not the person. Privacy-friendly and resurgent as third-party cookies decline.
Demographic & geo	Targets by age, gender, income, location and language.
Behavioural / audience	Targets people based on past browsing, interests and intent signals, organised into audience segments.
Retargeting / remarketing	Re-engages users who already interacted with the brand — visited the site, viewed a product, abandoned a cart — by showing them tailored follow-up ads. Typically the highest-converting programmatic tactic.
Lookalike / similar	Finds new users who resemble a brand's existing customers, using platform modelling on seed audiences.
First / second / third-party data	First-party: the brand's own data (CRM, site visitors). Second-party: another company's first-party data shared directly. Third-party: aggregated data bought from data providers (in decline with cookie deprecation).

The privacy shift. With third-party cookies being phased out and mobile identifiers restricted, targeting is moving toward first-party data, contextual signals, and privacy-preserving approaches (clean rooms, Google's Privacy Sandbox, cohort- and consent-based models).

10. Platforms & the tech stack

The systems advertisers use to plan, buy and measure.

Platform	Role
DSP	Demand-Side Platform — the advertiser's buying cockpit for programmatic. Examples: Google Display & Video 360 (DV360), The Trade Desk, Amazon DSP, Yahoo, Xandr.
DMP	Data Management Platform — collects, segments and activates audience data for targeting.
CDP	Customer Data Platform — unifies first-party customer data into persistent profiles for marketing and measurement.
Ad server (buy side)	Hosts creatives, controls delivery and provides independent measurement (impressions, clicks, conversions).
Measurement & attribution	Verification (viewability, brand safety, fraud), attribution models and incrementality testing that connect spend to outcomes.
Walled gardens	Closed ecosystems (Google, Meta, Amazon, TikTok) that combine inventory, data and buying tools in one environment.

---

11. How an ad auction works — end to end

Everything above, in the order it happens when a page loads.

1. A user opens a page or app. An ad slot needs to be filled.
2. The publisher's ad server / header bidding wrapper requests demand and passes the opportunity to its SSP(s).
3. The SSP builds an oRTB bid request describing the impression and sends it to ad exchanges and DSPs.
4. DSPs evaluate the request against their advertisers' targeting, budgets and audience data, and return bid responses with a price and creative.
5. The auction runs. Deal-based demand (PG, PD, PMP) is prioritised per the publisher's rules; otherwise the highest open-auction bid above the floor wins.
6. The winning creative is served to the user, and impression, viewability and click data flow back to both sides for reporting and billing.

All of this — request, auction, decision, render — typically completes in well under half a second, and repeats for every ad slot on every page, billions of times a day.

12. Glossary of acronyms

Every acronym on this page — CPM, RTB, oRTB, SSP, DSP, PMP and more — is defined in the standalone glossary.

AdTech Glossary — a quick-reference index of every term used across this wiki. Open the Glossary →

↑ Back to top