Asynchronous Tagging

One of the many methods through which Tealium improves site performance is by using asynchronous loading of tags. This method is becoming increasing popular, especially after Google’s adoption of asynchronous tags in 2010 for its analytics product. Tealium is one of the pioneers in asynchronous tracking, first adopting the methodology for tag management back in 2008.

But what exactly is asynchronous tracking and how does it improve site performance?

Before explaining the asynchronous method, it is important to note how tags load and why they slow down web sites. Most tags today are loaded in synchronous manner (think serial). When a page loads a synchronous tag, it waits for the tag content to load before moving on to the next content. The figure below shows an example of a page loading 4 tags in a synchronous or serial manner. The page starts by loading the first tag. After the tag has been completely loaded, the page moves on the second tag. The process is then repeated for the ensuing tags. Assuming each tag takes half a second to load, we’re looking at a total load time of 2 seconds to load all 4 tags.

Synchronous tags

Synchronous Tag Loading

With asynchronous tracking, the browser can load the different tags in parallel. It no longer has to wait for a certain tag to load completely before moving on to the next or the rest of the page content. This is shown in the figure below. Using our example of the page with 4 tags, we can see that the browser starts downloading the 4 tags in parallel, completing the process much faster. The 4 tags in this case are completed in a fraction of a time compared to the synchronous method.

Asynchronous tag loading

Asynchronous Tag Loading

Asynchronous tracking has many benefits. One obvious benefit is improved site performance, as demonstrated above. Another benefit is improved tracking and data accuracy.  Because tags are loading in parallel to the rest of the content, they can be placed on top of the page, which improves the accuracy of data being collected.

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