Viewability glossary

Viewability is the ability for a digital ad to be seen by an actual consumer. To be considered viewable, an ad must meet the minimum guidelines set by the industry, and illegal bot traffic and other forms of ad fraud should never be included in the number of viewable impressions. Viewability does not describe how effective an ad was, whether it was seen by target audiences, or even if it was seen at all. For more on viewability, check out our guide.

Ad stacking
Placing multiple ads on top of each other in a single placement, with only the top ad being viewable.

Above the fold (ATF) 
Ads that are placed on a web page where they are immediately viewable (no need to scroll down further).

Ad exposure time
The time an ad was in view.

Below the fold (BTF)
Ads that are placed further down a page that require a consumer to scroll down in order to see it.

Click-based metrics
Measurement based on the number of consumers who click on digital content. Includes metrics like clickthroughs, click-through rates.

Home page takeover
An advertising campaign that uses all available ad space, and potentially other specialized inventory, to “take over” a website’s index page. “Takeover” is a bit misleading because it’s rarely every ad slot on a page; it’s often a masthead or rich media creative plus a companion or two. This is also known as roadblocking.

Iframe
An in-line frame containing an ad within a web page. An iframe can be friendly or unfriendly (cross-domain).

Friendly iframe
An iframe that shares the same domain as the main page it’s hosted on.

Cross-domain iframe
An iframe where the iframe and the parent page have a different  domain. This is also known as an unfriendly iframe.

In-app
In mobile advertising, in-app refers to ads that are delivered to a consumer through an app on their mobile device (phone or tablet).

In-browser
In mobile advertising, in-browser refers to ads delivered to a consumer through the mobile browser (Chrome, Safari, etc.) rather than an in-app environment.

In-stream video ads
Video ads that play before (pre-roll), during (mid-roll), or after (post-roll) the publisher’s video content.

Interstitial ad
Full-screen or pop-up ads that cover the interface of their host application or a web page. They’re typically displayed at natural transition points in the flow of an application or web page, such as between activities or during the pause between levels in a game. When an app or web page shows an interstitial, the consumer has the choice to either tap on the ad and continue to its destination, or close it and return to the app or web page.

Measurability rate
The rate at which a given vendor can measure ads for viewability.

Measurable impressions
Impressions that can be measured for viewability. Not all ads served can actually be measured for viewability. This is because some ad environments can prevent measurement technology from accessing the information needed.

Measurement tag
A piece of code added to the creative in order to send data to the measurement provider so viewability can be determined.

Mobile Rich Media Ad Interface Definitions (MRAID)
A common API developed to enable rich media advertising in mobile in-app environments. MRAID is a standardized set of commands, designed to work with HTML5 and JavaScript, that developers creating rich media ads use to communicate what those ads do with the apps they are being served into – expand, resize, get access to device functionalities such as calendar events, etc. MRAID is only relevant for mobile rich media creatives that run in an in-app environment, not mobile web.

Out-stream video ads
A video ad that autoplays whenever a consumer navigates to it within text content. It’s known as outstream because the ad exists outside of online video content. Instead of running within a standard video player, these high-quality impressions can run within standard ad placements, on the corner of the page, or even within the content of a written article. Also known as in-read or native video.

Placement
The location where an ad will be placed. Different ad placements will have different viewability rates based on consumer activity, such as above the fold vs. below the fold.

Pre-bid
Occurring before the advertising media purchase takes place. In some programmatic environments, ad buying resembles an auction in which potential buyers place “bids” on desirable advertising inventory. A brand or agency may want to know the likelihood that inventory will meet certain criteria (such as viewability) before bidding on it – that is, pre-bid. Pre-bid viewability is a best estimate that an ad will be viewable but does not guarantee it.

Rich media
An ad that includes advanced features like video, audio, or other elements that encourage viewers to interact and engage with the content. The ad can expand, float, peel down, etc.

Video Ad Serving Template (VAST)
A script that gives video players information for serving ads.

Video Player Ad-Serving Interface Definition (VPAID)
A definition that establishes a common interface between video players and ad units, enabling a rich interactive ad experience.

Viewability
The ability for an ad to be seen by a consumer. In order to be considered “viewable,” an ad must meet the minimum requirements in the MRC guidelines.

Viewport
The consumer’s visible area of a web page. It varies by device.