A zone tag is the code chunk that places your ad item on a page. It passes along the ad item information, and usually some extra information, for tracking and display.

Choosing the right type is important because, depending on the situation, your ad item may not show or you may miss some features if the zone isn’t properly configured. See below for a breakdown of characteristics for each different zone tag.

Asynchronous Javascript (Async)

An Asynchronous Javascript tag will reference the incoming ad item and adjust the zone to serve accordingly. For example, if an image-based ad is chosen, it will display inside of an HTML image tag. If a custom HTML ad item is chosen to serve, it will render the ad in an iFrame. Asynchronous Javascript tags are loaded independently of the page contents and do not interfere with the load time of the page.

Asynchronous 1.1 (Beta)

The Async Beta tags are used to render ads asynchronously via JavaScript however does not require the document.write method of drawing to the page. Instead, the Async Beta tag will render directly to the placement container DIV.

This is particularly useful in cases like infinite scrolling sites where document.write may cause conflicts with white pages or empty spots.

Javascript

If you need custom HTML code served inline with the page content (ie. outside of an iFrame), or when a publisher's website causes conflicts with asynchronous tags, you may need to use a JavaScript tag. These tags will serve properly when a zone has its size set as "responsive".

iFrame & iFrame (HTML Only)

Both of these tags will serve almost identically, except the HTML iFrame will not run javascript. It is generally recommended to use these tags ONLY when your publisher has requested them. iFrame tags load content securely and are unable to interact with the page it is displayed on. iFrames also load asynchronously.

Image (Basic)

This will serve an HTML image tag wrapped in a hyperlink tag to direct users when they click.

JSON Ad API

When using a JSON Ad API tag, an ad request will return a JSON object. The JSON response contains all the base details needed to display an ad item. The JSON response will include the ID of the ad item, the destination for the click and the location of the image, as well as the dimensions and any other settings you’ve set for the ad item and will be rendered/styled according to the HTML/CSS or Javascript included on the page.

AMP

These tags are lightweight, easy to use, and are AMP compliant to allow mobile sites to load as quickly as possible. There are two cases where you'll have to modify your AMP tags before they can serve, which you can read about here.