Header Bidding Glossary

Ad Formats

This section contains terms around ad formats and their respective configuration.

MediaType or Media Format

banner - also called ‘display’, these ads are generally simple rectangular images.

native - the components of this mediatype like text, links, and images are all separated so they can be formatted to smoothly fit into the content.

video - see Player-Initiated Video and Page-Initiated Video

Multiformat AdUnit

An AdUnit that can display creatives of multiple media formats: banner, native, and/or video.

Page-Initated Video

Also called ‘outstream’, these are ads that can share an AdUnit in Prebid.js with banners, but are displayed with a special ‘renderer’ to play a video ad instead of a static image. Unlike ‘player-initiated’ units (aka ‘instream video’), this renderer only renders the ad and does not show content.

Player-Initiated Video

Once called ‘instream’, these are AdUnits that are rendered in a video player before, during or after content.


Interstitial ads are full-screen ads that cover most of the visible UI. They’re typically displayed during navigation, e.g. clicking a link or going to the next level in a game.

Ad Tech Industry

Ad Server, SSPs, DSPs, etc.

Client Side Header Bidding

The auction takes place on the client device of the user. Prebid.js is a client side bidding solution.

Direct Sold Ads

Ads sold by a publisher’s sales staff and entered directly into the ad server.

Interactive Advertising Bureau (IAB)

The IAB is the ad tech industry standards body.

Programmatic Ads

Ads delivered either through an open marketplace through an auction, or as a pre-arranged “deal” that was initiated through systems outside of the publisher’s ad server.

Server Side Header Bidding

The header-bidding auction takes place on a server. Notable server side bidding systems are

Ad Server

A system that allows a content publisher to manage their portfolio of ads and deliver those ads according to the defined targeting and pacing rules.


A ‘placement’ is bidder term that’s similar to AdUnit – it helps the bidder link the AdUnit to details about the header bidding auction that have been entered into their systems. Some bidders may use a combination of multiple parameters like zoneId, formatId, siteId or something else, but the concept is similar.

A notable exception is Google Ad Manager. Google Ad Manager placements are a group of ad units!

Line Items

A ‘Line Item’ is an ad server concept that contains information about how a specific ad is intended to serve to a website or app. Line items are added to containers called ‘Orders’ and carry details like:

  • The number of times the advertiser or buyer wants an ad creative to serve
  • The cost negotiated for the campaign
  • Start and end times of the campaign
  • Targeting that allows the advertiser or buyer to reach its intended audience or demographic

(Adapted from the Google Ad Manager Line Item documentation)

Integrating Prebid bids with other ad sources requires a special line item setup if you aren’t using an ad server that supports Prebid natively, which most don’t. The Prebid Line Item Manager can help set up GAM line items. GAM 360 has the beginnings of a native Prebid integration.

Key Values

A generic way to target line items in your ad manager. Prebid makes heavy use of key values to indicate the winning bidder and the winning bid price.


A description of the context where an ad may be served.


The ‘hole’ in the web page or mobile app where an ad may appear. This is very similar to AdUnit, but is the technical implementation defining which ad sizes and formats may appear within it.

e.g. With the”Google Publisher Tag” (GPT) library, the “defineSlot()” function call maps an HTML div - this is the technical implementation and is referred to as the AdSlot. The defineSlot() function maps the div to the GAM AdUnit which is the sellable item that shows up in the ad server user interface.


Ad servers such as Google Ad Manager - the AdUnit is the thing that business people care about. It’s an inventory concept targeted by line items.

Prebid Adunit - Prebid adds another layer to the ad server AdUnit: which header bidders should participate in the auction and their parameters.


Accelerated Mobile Pages (AMP) is an alternate web platform that can speed web pages on mobile devices, but also limits the scripts that can be run on the page. See Prebid’s AMP page


A Global Placement ID (GPID) is a unique ad slot identifier. e.g. on infinite scroll pages the same sized adunit may be dynamically created each page that the user scrolls. On the 5th instance of a given adunit, the unique GPID might be /home/med-rect#5.


Deprecated - this was Prebid’s attempt at a unique placement ID before GPID came around.


Open Real Time Bidding is a protocol defined and managed by the IAB for transacting programmatic ad auctions.

Billing URL (burl)

A URL provided by a bidder requesting to be notified when their bid has been rendered. Prebid.js creates a pixel with this URL just before the BID_WON event.

Loss URL (lurl)

A URL provided by a bidder requesting to be notified when their bid did not win the auction. Prebid does not do anything with loss URLs.

Notice URL (nurl)

A URL provided by a bidder as an alternate source of the creative. See the nurl FAQ entry for Prebid-specfic details.

Prebid Mobile

Prebid SDK and Prebid Server working together to provide header bidding for mobile apps.

Config ID

When coding the mobile app for the technical implmentation of the adslot, the SDK function call refers to this ID that refers to an impression-level stored request on Prebid Server. This server-side stored request contains the bidders and parameters that can participate in the auction for that adslot.


A library from a vendor that can display creatives of a special type, e.g. video or rich media.

Prebid Server

Header bidding on the server.

Account ID

Prebid Server host companies may give out account IDs to publishers for authorization, configuration, and reporting purposes. This account ID is provided on s2sConfig when utilizing Prebid Server from Prebid.js and in the init function when utilizing Prebid SDK.

Stored Request

impression-level stored request - a block of JSON available to Prebid Server that stores the bidders and parameters associated with a particular adslot. There’s a string ID for this block of JSON that can be used by the Prebid SDK (see Config ID) or Prebid.js.

top-level stored request - a block of JSON available to Prebid Server that stores global parameters like timeout, price granularity, targeting parameters, etc. There’s a string ID for this block of JSON that can be used by the Prebid SDK or Prebid.js. In Prebid SDK, the “account ID” field in the init function currently doubles as the ID of the top-level stored request.

AMP stored request - a block of JSON available to Prebid Server that stores both global and impression-level parameters. There’s a string ID for this block of JSON that can be used by AMP RTC calls.


Header bidding in javascript on a web page.


A piece of javascript that can display creatives of a special type, e.g. video or rich media.