A zone tag is a snippet of code that places your ad item on a publisher's webpage or app. It passes along information about an ad item, and usually other details such as ones needed to track the ad's performance.

Choosing the right type of zone tag is important because your ad item may not show or you might miss some features if you didn't use the appropriate zone tag for your needs.

Asynchronous JavaScript (Async)

All new zones are set to use asynchronous JavaScript by default. We recommend using it unless you specifically require another type of zone tag.

An asynchronous JavaScript tag adjusts the zone based on the file type of the incoming ad. For example, if an image-based ad is chosen, it will display inside an HTML image tag. If on the other hand a custom HTML ad item is chosen, it will render the ad in an iFrame.

Another feature of asynchronous JavaScript tags is that it allows ads to load independently of the page contents, which means it doesn't affect the load time of the page.

Note: If you are serving an ad to a zone that has a size set to responsive, you cannot use an Async tag. You must use a JavaScript or Image (Basic) tag.

Asynchronous 1.1 (Beta)

Async Beta tags are used to render ads asynchronously via JavaScript. However, it 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 infinitely 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 (i.e. outside of an iFrame), or when website content causes conflicts with asynchronous JavaScript tags, you may need to use a JavaScript tag. These tags will serve properly when a zone has its size set to be responsive.

This zone tag is synchronous, meaning it will ask the webpage to wait for the ad to load before loading the rest of the page's content. Normally, this delay is so small it doesn't affect the website visitor or app user's experience. But if a zone is set for programmatic bidding, the delay will usually be compounded, leading to a noticeable delay in loading time. We recommend using Async tags for such zones.

iFrame & iFrame (HTML Only)

These tags serve ads in a similar way, expect the HTML Only iFrame will not run JavaScript. iFrame tags load content securely and are unable to interact with the page it is displayed on. iFrames also load asynchronously.

Note: iFrames may not serve properly within zones that have a size set to be responsive.

Image (Basic)

This is an HTML image tag wrapped in a hyperlink tag to direct users when they click on an ad.

The default behavior of many modern browsers will be to block any clicks associated with these tags, unless this option has a third-party cookie installed that allows the click to function.

JSON Ad API

This type of zone tag is not recommended unless you need to heavily customize when or how your ad is rendered because they add more steps to the process compared to other tag types. 

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 items and will be rendered/styled according to the HTML/CSS or JavaScript included on the page.