Ad tech glossary

Plain-English definitions of the terms publishers meet in dashboards, contracts and auctions.

Read: What is an SSP?Estimate earnings

A B C D E F H I N O P R S V

Ad exchange: A digital marketplace where publishers' ad impressions are bought and sold in real time, usually through auctions between many buyers and sellers.
Ad network: A company that buys inventory from many publishers and resells it to advertisers, often in packages. It typically sets prices itself rather than running an open auction for each impression.
Ad unit: One ad placement on a page or app, such as a 300×250 sidebar slot. Each ad unit has its own tag and its own reporting.
ads.txt: An IAB Tech Lab text file at the root of a website that lists which companies are authorised to sell its ad inventory. Buyers check it to avoid counterfeit inventory.
app-ads.txt: The mobile-app version of ads.txt, hosted on the developer website listed in the app store.
Bid request: The message an SSP sends to buyers describing an available impression: page, ad size, device, approximate location and other signals.
Bid response: A buyer's reply to a bid request, with a price and the ad creative to show if it wins.
Brand safety: Practices that keep ads away from content an advertiser considers harmful or unsuitable for their brand.
Clearing price: The price actually paid for an impression after the auction ends. In a first-price auction it equals the winning bid.
CPC (cost per click): A pricing model where the advertiser pays only when a user clicks the ad.
CPM (cost per mille): The price for one thousand ad impressions. A $2 CPM means $2 for every 1,000 impressions.
CTR (click-through rate): Clicks divided by impressions, shown as a percentage. 5 clicks from 1,000 impressions is a 0.5% CTR.
DSP (demand-side platform): Software advertisers and agencies use to buy impressions automatically across many SSPs and exchanges.
eCPM (effective CPM): Earnings per 1,000 impressions regardless of pricing model: (earnings ÷ impressions) × 1,000. Useful for comparing formats and networks.
Fill rate: The share of ad requests that actually received an ad: filled impressions ÷ ad requests.
First-price auction: An auction where the winner pays exactly what it bid. Most programmatic display auctions now use first-price.
Floor price: The minimum price a publisher will accept for an impression. Bids below the floor are rejected.
Frequency cap: A limit on how many times the same user sees an ad or ad format within a period.
Header bidding: A technique where several demand sources bid on an impression at the same time before the ad server picks a winner, increasing competition.
Impression: One showing of an ad to a user. Most earnings reports start from impressions.
Interstitial: A full-screen ad shown between pages or app screens, with a close button.
IVT (invalid traffic): Impressions or clicks that do not come from genuine human interest, such as bots, data-centre traffic or accidental clicks. It is filtered before payment.
Native ad: An ad assembled from parts (title, image, text) and rendered in the host site's style, labelled as sponsored.
OpenRTB: The IAB Tech Lab protocol (versions 2.5 and 2.6 are common) that defines how bid requests and bid responses are formatted between SSPs and DSPs.
Popunder: An ad that opens in a new window or tab behind the current page, usually triggered by a click.
Programmatic advertising: Buying and selling ads automatically through software and auctions instead of manual insertion orders.
Revenue share: The split of ad revenue between the publisher and the platform. With a 70/30 share, the publisher receives 70% of gross revenue.
RPM (revenue per mille): Publisher earnings per 1,000 page views (not impressions). It includes the effect of having several ads per page.
RTB (real-time bidding): An auction for each individual impression that finishes in milliseconds while the page loads.
sellers.json: An IAB Tech Lab file published by SSPs and exchanges that lists the sellers they represent, so buyers can verify the supply chain alongside ads.txt.
SSP (supply-side platform): Software that publishers use to sell their ad inventory to many buyers through real-time auctions, with controls such as floor prices and quality filters.
VAST: Video Ad Serving Template, the IAB standard that tells a video player which ad to play and how to track it.
Viewability: Whether an ad had a real chance to be seen. The common display standard is 50% of the ad's pixels in view for at least one second.