AdTech glossary

The real barrier to entry in this industry is acronym density, not difficulty. 40 terms, defined without marketing language, each linked to the articles that use it.

Ad exchangealso: exchange: The auction venue where bid requests meet bids. Historically distinct from an SSP; in practice the same companies now run both.; See also: ssp, openrtb, first price auction
Ad Request: The call a publisher page or app makes asking for an ad to fill a slot. One request can fan out to dozens of bid requests.; Advertising TechnologySee also: bid request, ad server
Ad Server: The system of record that decides which creative renders in a slot, then logs the delivery. Publishers and advertisers each run their own, which is why their numbers differ.; Advertising TechnologySee also: ad request, discrepancy
ads.txt: A public file at a domain root listing who is authorised to sell its inventory. The simplest defence against domain spoofing.; See also: spo, sellers json
AdTech taxalso: take rate, the tax, tech tax: The share of advertiser spend absorbed by intermediaries before it reaches a publisher — commonly 35–50% in the open auction. Fees compound rather than add, because each party charges on what reaches it.; Curation and Supply-Side TargetingSee also: take rate, spo, supply path
Advertiseralso: brand, buyer: The party with the budget and the thing to sell. Buys attention; sets the KPI everything downstream is judged against.; Advertising TechnologySee also: publisher, dsp
Attribution: Assigning credit for a conversion to the touchpoints before it. Every model is a simplifying assumption, none is ground truth.; The Marketing Funnel Marketing Mix Modelling Comes BackSee also: incrementality, mmm, discrepancy
Bid Request: An OpenRTB payload describing one available impression: the user, the page, the slot, the floor. Sent to buyers, answered in under ~100ms.; How an RTB Auction WorksSee also: openrtb, dsp, floor price
Bid Shading: A DSP lowering its bid below true value to approximate what a second-price auction would have charged, using the historical price distribution for similar impressions.; First Price and the Rise of Bid ShadingSee also: first price auction, cpm
CPMalso: cost per mille, cost per thousand: Cost per mille: the price of one thousand impressions. Quoting in thousands is a print-media habit that stuck.; Advertising Technology The Marketing Funnel First Price and the Rise of Bid Shading Marketing Mix Modelling Comes BackSee also: impression, ecpm, take rate
Curationalso: curated marketplace, supply-side targeting: Packaging inventory into pre-approved deals on the sell side — selecting sites, applying quality thresholds, and increasingly layering audience data at the SSP rather than the DSP.; Curation and Supply-Side TargetingSee also: spo, supply path, clean room
Data Clean Room: A controlled environment where two parties query overlapping data without either exporting the other's raw rows. Output limits and noise stop re-identification.; Curation and Supply-Side Targeting The Cookie That Did Not Die Marketing Mix Modelling Comes BackSee also: uid2, attribution
Discrepancy: The gap between two systems counting the same campaign. Caused by different count points, timezones, and attribution windows, not usually by fraud.; See also: ad server, attribution
DSPalso: demand side platform: Demand-Side Platform. Software a buyer uses to bid on impressions across many exchanges under one budget, targeting and frequency policy.; Advertising Technology How an RTB Auction WorksSee also: ssp, bid request, bid shading
eCPM: Effective CPM: revenue divided by impressions, times 1000. Lets you compare a CPC or CPA deal against a CPM one.; See also: cpm
First-Price Auction: The winner pays exactly what it bid. Now the display default, which forces buyers to guess the clearing price rather than bid their true value.; How an RTB Auction Works First Price and the Rise of Bid ShadingSee also: second price auction, bid shading, floor price
Floor Price: The minimum a publisher will accept. Hard floors reject lower bids outright; dynamic floors move per request based on predicted demand.; How an RTB Auction Works First Price and the Rise of Bid ShadingSee also: first price auction, bid request
Header Bidding: Running a unified auction in the page before calling the ad server, so every demand source competes at once instead of in a waterfall.; First Price and the Rise of Bid ShadingSee also: prebid, waterfall, spo
Impression: One rendering of one ad to one user. The atomic unit that almost every adtech price, metric and log line is built on.; Advertising Technology How an RTB Auction WorksSee also: cpm, viewability, ad request
Incrementality: The conversions that happened only because of the ad, measured by holding out a randomised control group. The closest thing to causal truth in media.; The Marketing Funnel Marketing Mix Modelling Comes BackSee also: attribution, mmm
Invalid Trafficalso: IVT, ad fraud: Traffic not from a genuine user with genuine intent. GIVT is filterable by lists and rules; SIVT needs behavioural detection.; See also: viewability, ads txt
Marketing Mix Modelingalso: MMM, media mix modeling: Regressing aggregate sales on aggregate spend by channel. Privacy-proof because it needs no user-level data, and back in fashion for exactly that reason.; Marketing Mix Modelling Comes BackSee also: attribution, incrementality
OpenRTB: The IAB protocol that standardises bid requests and responses, so one DSP integration works across many exchanges.; How an RTB Auction WorksSee also: bid request, vast
Prebid: The open-source header bidding wrapper that became the de facto standard. Prebid.js in the browser, Prebid Server for server-side auctions.; See also: header bidding
Privacy Sandboxalso: sandbox: Google’s programme of Chrome APIs intended to replace third-party cookies. Retired on 17 October 2025 after low adoption and antitrust pressure; its APIs are being removed from Chrome through 2026.; The Cookie That Did Not DieSee also: third party cookie, topics api, uid2
Publisheralso: supply, seller: The party with the audience and the ad slots. Sells attention, and receives whatever survives the supply chain.; Advertising TechnologySee also: advertiser, ssp, ad server
Retail Media Network: A retailer selling ads against its own shopper data and surfaces. Closed-loop by construction: the same company sees the ad and the purchase.; The Marketing Funnel Marketing Mix Modelling Comes BackSee also: attribution, clean room
Second-Price Auction: The winner pays one cent above the runner-up. Makes honest bidding optimal, but became untenable once soft floors and header bidding made "second" ambiguous.; First Price and the Rise of Bid ShadingSee also: first price auction
sellers.json: The other half of ads.txt: an exchange publishing who its sellers are, so a buyer can trace the whole chain.; See also: ads txt, spo
Server-Side Ad Insertionalso: SSAI, ad stitching: Stitching ads into the video stream server-side so they play without buffering and cannot be blocked. Costs you client-side signal in exchange.; See also: vast
SSPalso: supply side platform: Supply-Side Platform. Software a publisher uses to expose inventory to many buyers and run the auction that picks a winner.; Advertising Technology How an RTB Auction Works Curation and Supply-Side TargetingSee also: dsp, first price auction, take rate
Supply pathalso: path, supply route: The specific route a bid request takes from a publisher to a buyer, including every SSP and reseller hop. Two paths to the same impression can differ by 20% in cost and by far more in quality.; Curation and Supply-Side TargetingSee also: spo, sellers json, ad tech tax
Supply Path Optimizationalso: SPO: Buyers deliberately reducing how many intermediaries they route through, to cut fees and duplicate auctions for the same impression.; Curation and Supply-Side TargetingSee also: header bidding, take rate, ads txt
Take Rate: The share of advertiser spend an intermediary keeps. Sum of all take rates along a path is the "adtech tax".; See also: spo, cpm
Third-Party Cookie: A cookie set by a domain other than the one being visited. The load-bearing identifier of web adtech for twenty years, now blocked by default in Safari and Firefox.; The Cookie That Did Not Die Marketing Mix Modelling Comes BackSee also: uid2, topics api, clean room
Topics API: Chrome's interest-based replacement signal: the browser reports a handful of coarse topics from recent browsing instead of exposing an identifier.; The Cookie That Did Not DieSee also: third party cookie
UID2: Unified ID 2.0: a deterministic identifier derived from a salted hash of an email or phone number, with consent, shared across the open internet.; The Cookie That Did Not DieSee also: third party cookie, clean room
VAST: Video Ad Serving Template: the XML a video player fetches to learn which creative to play and which tracking pixels to fire.; See also: ssai, openrtb
Viewability: Whether an impression had a real chance to be seen. The MRC bar for display is 50% of pixels for one continuous second.; See also: impression, ivt
Waterfall: Calling demand sources in sequence by historical average price until one fills. Cheap to run, leaves money on the table, mostly replaced by unified auctions.; See also: header bidding