Our new study into the effect of third-party tracking tags on site download times and data reporting was a bit of an eye-opener. In short, the main findings – which are covered in a Q&A with TagMan founder Paul Cook on Econsultancy here – were:

1) Tags really do slow down your page

The slowest-loading assets on site pages in our study were tracking tags, taking as much as 250ms. Based on our study, a delay of around one second causes approximately 10% of users to abandon the page, suggesting that four tags on the page could lose you 10% of your visitors.

2) Tag position needs careful consideration

If page load speeds are slow then very different figures will be reported depending on where tags are placed and the relative effect of the tag will be far less. In our test, hecklerspray.com achieved a 20% increase in the traffic reported by Google Anayltics when the tag was placed at the top of the page, which would be a good argument to put the code higher up the page.

3) Page optimisation is critical

The rate at which users abandon slow pages underlines the need to ensure they are written with a view to loading as quickly as possible. Both sites in the test contained third-party analytics tags that were no longer in use. An easy place to start would be to identify any tags that are no longer in use and remove them.

4) IFrame container tags suffer the most

The worst performing method of including tags in the page was via an invisible iFrame at the bottom of the page – the method used by the major container-tag solutions. The tests showed the most effective way to collect data is by using a blank JavaScript call, particularly if the tracking code is placed at the end of the page.

There’s a summary of the findings here and, to get a copy of the full report, complete with all the results and the code Paul used to run the test, email us at contact@tagman.com

I was at a client meeting this week an the question of page download came up so I thought I’d jot down the answer here. TagMan consists of a JavaScript library and short amount of code that is included in each page. The library is standardised and shared across all clients so that users only download it once per session.

To prevent tags from slowing down the page, you can configure TagMan to writes out into an iframe instead of directly into the page.  The advantage of writing tags out into an iframe is they will not delay the page from completing like Javascript does.  If the business logic dictates that no 3^rd party tags need to be served, minimal code is sent back to the page, keeping bandwidth to an absolute minimum and reducing the impact on page download speed.  However, if page weight remains an issue you can always store a lightweight configuration in TagMan that you can roll back to in case of an emergency.