Ad Tech Glossary
Ad tech is full of acronyms. This ad tech glossary explains 94 terms every publisher meets, from ads.txt and CPM to header bidding and supply path optimization, in plain English. Jump to a letter, or use your browser’s search to find a term.
A
A/B test (ad test)
Showing two versions of an ad setup, such as two layouts or floor prices, to similar visitors and comparing the results. Always compare revenue per page view, not only CPM.
Ad blocker
Browser software or an extension that stops ads from loading. Blocked ads earn nothing, so a high ad block rate lowers your revenue per visit.
Ad exchange
A marketplace where publishers’ ad space is sold to advertisers in real-time auctions. Google AdX, Magnite and PubMatic run large exchanges.
Ad inventory
All the ad space a publisher can sell, usually counted in impressions per month.
Ad network
A company that buys ad space from many publishers and resells it to advertisers, often as a package. AdSense is the best-known example.
Ad refresh
Loading a new ad in the same slot after a set time or user action. It can raise impressions, but refreshing too fast lowers viewability and can break ad partner rules.
Ad request
The call a web page makes to an ad server or exchange to get an ad for a slot.
Ad server
Software that decides which ad to show in each slot, based on campaigns, prices and rules. Google Ad Manager is the most used publisher ad server. See Google Ad Manager guide.
Ad stack
All the tools a publisher uses to sell ads: ad server, header bidding wrapper, SSPs, consent tool, analytics and more.
Ad unit (ad slot)
A defined place on a page where an ad can appear, such as a 300×250 sidebar box. See banner ad sizes.
ads.txt
A public text file on a website that lists which companies are allowed to sell its ad space. It protects publishers and buyers from fake inventory. See ads.txt generator.
AdSense
Google’s ad network for websites. It is easy to start with and needs no traffic minimum, but gives publishers less control than an ad server setup. See how to apply for AdSense.
AdX (Google Ad Exchange)
Google’s ad exchange, sold as part of Google Ad Manager. Smaller publishers usually get access through a partner using MCM.
Anchor ad (sticky ad)
An ad that stays fixed at the top or bottom of the screen while the user scrolls. It usually has high viewability.
app-ads.txt
The mobile app version of ads.txt. App developers host it on their website to authorize sellers of their in-app ad space.
B
Bid floor (floor price)
The lowest price a publisher accepts for an impression. Bids below the floor lose.
Bid rate
The share of bid requests a bidder answers with a bid. A bidder with a very low bid rate adds delay without adding revenue.
Bid request
A message sent to buyers describing an available impression, such as page, size, device and consent, so they can decide whether to bid.
Bid response
A buyer’s answer to a bid request, containing the price and the ad.
Bid shading
A buyer-side technique that lowers bids in first-price auctions to avoid paying more than necessary.
Brand safety
Steps that keep ads away from content an advertiser doesn’t want to appear next to, such as violence or adult topics.
C
Click-through rate (CTR)
Clicks divided by impressions. Display ads usually have a CTR well below 1%. A sudden spike can be a sign of invalid traffic.
Client-side header bidding
Header bidding where the auction runs in the visitor’s browser. It is transparent and easy to start, but each bidder adds page weight.
CLS (Cumulative Layout Shift)
A Core Web Vitals metric that measures how much a page jumps while loading. Ads that load without reserved space are a common cause. See Core Web Vitals and ads.
CMP (Consent Management Platform)
The tool that shows the cookie banner, records each visitor’s consent choices and passes them to ad partners. See consent requirements.
Consent string
A coded record of a visitor’s consent choices, created by the CMP under the TCF framework and read by ad partners.
Contextual targeting
Choosing ads based on the content of the page rather than data about the user. It works without cookies.
Core Web Vitals
Google’s page experience metrics: LCP for loading, INP for responsiveness and CLS for visual stability.
CPA (cost per action)
A pricing model where the advertiser pays only when a user completes an action, such as a sale or sign-up.
CPC (cost per click)
A pricing model where the advertiser pays for each click on an ad.
CPM (cost per mille)
The price of 1,000 ad impressions. It is the standard price unit in display advertising. See CPM calculator.
CPV (cost per view)
A video pricing model where the advertiser pays for each qualifying view.
CTV (connected TV)
Television watched through an internet-connected device, such as a smart TV or streaming stick. CTV ads are sold programmatically, often at high CPMs.
Curation
Packaging inventory from many publishers into ready-made deals for buyers, often by an SSP or a third-party curator.
D
Deal ID
A code that identifies a private deal between a publisher and a buyer, so the ad server can apply the agreed price and rules.
Demand
The advertisers and buying platforms that bid on a publisher’s ad space.
DIRECT (ads.txt)
The ads.txt label for a seller account that the publisher itself owns and gets paid through. See reseller to direct.
Discrepancy
The difference between impressions or revenue counted by two systems, such as your ad server and an SSP. Up to about 10% is common.
DSP (demand-side platform)
Software that advertisers and agencies use to buy ad space across many exchanges. The Trade Desk and Google DV360 are examples.
E
eCPM (effective CPM)
Revenue per 1,000 impressions, calculated after the fact. It lets you compare earnings from CPM, CPC and other pricing models. See RPM vs CPM vs eCPM.
F
Fill rate
The share of ad requests that receive an ad. Unfilled requests earn nothing.
First Look
A former Google rule that let AdX win an impression before other exchanges could compete. It was ruled illegal in the US antitrust case. See Google ad tech antitrust case.
First-party data
Data a publisher collects directly from its own visitors, such as logged-in user information or reading behavior.
First-price auction
An auction where the winner pays the price it bid. Most programmatic auctions have used this model since 2019.
Frequency capping
Limiting how many times the same user sees an ad in a given period.
G
Google Ad Manager (GAM)
Google’s ad server and ad exchange platform for publishers, formerly DoubleClick for Publishers (DFP) and AdX.
H
Header bidding
A method where several buyers bid on an impression at the same time before the ad server is called. It usually raises revenue compared with a waterfall. See AdSense vs header bidding.
I
IAB
The Interactive Advertising Bureau, the industry body that publishes standards such as ad sizes, VAST, ads.txt and OpenRTB.
Impression
One display of an ad to a user. Most ad pricing is based on impressions.
In-feed ad
A native ad placed between items in a list or feed, such as between article teasers.
Interstitial
A full-screen ad shown between pages or screens. Google limits intrusive interstitials on mobile.
Invalid traffic (IVT)
Impressions or clicks that don’t come from real, interested people, such as bots or accidental clicks. Advertisers don’t pay for them, and too much can get an account limited. See ad serving limited.
K
Key-values
Custom labels sent with ad requests, such as page category, so the ad server can target campaigns more precisely.
L
Last Look
A former Google rule that let AdX see the highest rival bid and then beat it. It was ruled illegal in the US antitrust case.
Lazy loading
Loading an ad only when its slot is about to scroll into view. It improves page speed and viewability.
Line item
A rule in an ad server that defines which ads run, where, when and at what price. Header bidding setups often use many line items, one per price bucket.
M
MCM (Multiple Customer Management)
Google’s program that lets approved partners manage Ad Manager and AdX access for other publishers.
N
Native advertising
Ads that match the look and feel of the content around them, such as sponsored articles and in-feed units. See native advertising examples.
O
Open auction
The public programmatic auction where any approved buyer can bid on available impressions.
Open Bidding
Google’s server-side auction inside Ad Manager, where third-party exchanges compete with AdX. It was formerly called Exchange Bidding. See Open Bidding explained.
OpenRTB
The IAB standard format for bid requests and responses in real-time bidding.
P
Page RPM
Revenue per 1,000 page views. It is the best single number for comparing ad setups, because it includes how many ads each page shows. See ad revenue calculator.
Pageview
One load of a web page by a visitor. A pageview can contain several ad impressions.
PMP (private marketplace)
An invite-only auction where a publisher offers selected inventory to chosen buyers, often at a higher floor.
Prebid Server
The server-side version of Prebid. It moves bidder calls off the page to keep it fast.
Prebid.js
The leading open-source header bidding library. It runs the auction between bidders in the browser. See Prebid.js setup guide.
Preferred deal
A deal where a buyer gets first chance to buy inventory at a fixed price before the open auction.
Price granularity
How finely header bidding prices are rounded into ad server line items, such as steps of $0.01, $0.10 or $0.50.
Programmatic advertising
Buying and selling ads automatically through software and auctions instead of manual orders.
Programmatic guaranteed
A deal with a fixed price and a guaranteed number of impressions, delivered through programmatic tools.
Publisher
A website, app or media company that sells ad space next to its content.
R
Real-time bidding (RTB)
Selling each impression in an automated auction that takes place in milliseconds while the page loads.
RESELLER (ads.txt)
The ads.txt label for an account owned by a company that sells the publisher’s inventory on its behalf.
Rich media
Interactive ads with video, animation or expanding elements.
RPM (revenue per mille)
Publisher earnings per 1,000 page views or impressions, after the platform’s share.
S
Second-price auction
An auction where the winner pays just above the second-highest bid. It was the standard before the move to first-price auctions.
sellers.json
A public file published by SSPs and exchanges that lists the publishers and intermediaries they work with. See ads.txt and sellers.json.
Server-side header bidding
Header bidding where the auction runs on a server instead of in the browser. It is faster for users but can match fewer cookies. See server-side header bidding.
SPO (supply path optimization)
When buyers choose the shortest and cheapest routes to an impression and drop duplicate or resold paths.
SSP (supply-side platform)
Software publishers use to sell ad space to many buyers through auctions. Examples include Magnite, PubMatic, Index Exchange and OpenX.
Supply chain object (schain)
Data passed in a bid request that lists every company that handled the impression, so buyers can see the full path.
T
Take rate
The share of ad spend kept by an ad tech platform as its fee.
TCF (Transparency and Consent Framework)
The IAB Europe standard that CMPs and ad partners use to record and share user consent in the EU.
Third-party cookie
A cookie set by a domain other than the site the user is visiting. Ad tech has used them to track and target users across sites.
Timeout
How long the header bidding auction waits for bids before sending the result to the ad server. See timeout calculator.
U
Unified pricing rules
Former Google Ad Manager rules that stopped publishers setting a higher floor for AdX than for other exchanges. They are being removed after the antitrust ruling.
Universal ID
A shared user identifier, such as UID2 or ID5, that ad tech uses as an alternative to third-party cookies.
UTM parameters
Tags added to a link so analytics tools can record where a visit came from. See UTM builder.
V
VAST
The IAB standard that tells a video player which video ad to play and how to track it.
Viewability
Whether an ad could actually be seen. Under the common standard, at least 50% of a display ad must be on screen for one second.
W
Waterfall
The older setup where ad networks are asked one after another in a fixed order until one fills the slot. Header bidding largely replaced it.
Win rate
The share of a bidder’s bids that win the auction.
Wrapper
A managed or packaged version of Prebid that handles bidders, settings and reporting for the publisher.
Y
Yield optimization
Everything a publisher does to earn more from the same traffic, such as testing floors, layouts and demand partners.
Learn more
Want to put these terms to work? Start with RPM vs CPM vs eCPM, read how publishers move from reseller to direct, or try our free ad tools.