If you’re a blogger or professional publisher monetizing your site through some form of display advertising, you’ve more than likely come across the terms “asynchronous” and “synchronous” ad tags in reference to display, mobile and video advertising.
Understanding how webpages load
To explain the difference between asynchronous vs synchronous ad tags, let me first talk about the basic structure and framework of a web page.
When a reader visits your website, in the time it takes for your page to load, all of those components load from top to bottom. So, if you have a piece of CSS styling code, or a synchronous ad tag, the page will not load until that piece of code loads. This can lead to increased page latency.
Asynchronous ad tags load independently of other page elements.
Synchronous ad tags load sequentially with the rest of the content on your page.
Asynchronous vs. synchronous ad tags in action
If you have a 728×90 leaderboard ad tag at the top of your website, it would be one of the first things to load. If you are using synchronous ad tags, that ad tag will load as the page loads, from top to bottom.
If you were using an asynchronous ad tag, that ad tag would actually “live” in an iFrame separate from your webpage, allowing it to load independently of your page. We recommend asynchronous ad tags because they allow the publisher’s page to load faster and give your readers a better experience with your webpage.
So, an asynchronous ad tag is a third party tag which is loaded by the browser independent to the rest of the content page, resulting in faster page load time in case the tag call is blocked or dropped.
Synchronous ad tags do not rely on iFrames and live right on your webpage, loading with the rest of the content and styling on your webpage.
Wondering if you have asynchronous vs synchronous ad tags? Unless you specifically requested synchronous ad tags, all Sovrn publishers are issued asynchronous ad tags by default when signing up.