Getting started: Ad units

Last updated on January 11, 2018

An ad unitThe smallest inventory component that represents the space on a site where ads display. is the specific place on your siteAn OpenX component that represents top-level domains or subdomains and is used to organize ad units. Sites enable you to target and report on inventory performance. where you want to display an ad. Create an ad unit for every location on your site where an ad should be served. You can see ad units in at the bottom of the diagram below.

If you're an OpenX Ad ServerA complete digital advertising platform where publishers sell, manage, and deliver their advertising inventory across all digital formats. user and you'd like to see how ad units relate to OpenX Ad Server as a whole, click here or on the diagram below.

Ad unit size

Each standard ad unit is a certain size, measured in pixels. A 728 x 90 ad unit is 728 pixels wide and 90 pixels high. OpenX also supports flexible ad units. Flexible ad units accept creatives of more than one size.

How ad units work

Each ad unit has a unique identifier and belongs to a single site.

When you create an ad unit in OpenX, you will receive an ad tagA small piece of code that defines the ad space where ads display on a website. It includes parameters that describe the inventory advertising campaigns can target, which may in turn display ads in the ad space., a piece of code to put in your website's source code. When a viewer loads the page, the ad tag communicates to OpenX and requests an ad that fits in the space allotted to it. This request is called an ad call. OpenX then finds an eligible ad and sends it to the ad tag. The ad tag puts the ad in the ad unit, and the viewer sees the ad.

For more detailed information on how a specific ad is selected, see Ad selection.

Ad unit inventory types

There are various inventory types for your ad units. Here is a brief explanation of each:


Are you ready to create ad units?

Create ad units

Create flexible ad units


This topic applies to Ad Server.