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What's the Difference Between Asynchronous and Synchronous Ad Tags?

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.

Think of your web page like a shingle on your house. You can put it up, take it down, style it, reinforce it and make it your own. Same thing as your website. You can build one yourself, style it with Javascript, CSS, HTML, etc. You can even make money from your website through models like display advertising, eCommerce, sponsored content, affiliate links, etc. All of these components live independently from each other on your website. More specifically, in your header.

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 with the meridian publisher platform.

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