Test the impact of ads and third party scripts

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Ben Schwarz

May 7, 2019

Calibre’s new ad blocking allows you to effortlessly monitor pages with or without ads and third party tracking scripts. Now you’re able to uncover how much impact ads have on performance without any code changes.

We’ve built uBlock, the worlds lightest Open Source ad blocker, right into Calibre. Blocking ads is available on all plans and can be enabled via Site → Settings → Test Profiles.


Why monitor without ads?

Tech-savvy individuals often use browser extensions to block ads. More often than not, it results in a much faster and less frustrating user experience.

Unfortunately, not everyone knows ad blockers exist or aren’t using browsers that are capable of running extensions to serve that purpose.

Seeing as many businesses rely on ad-revenue, it’s important to understand the huge impact both ads and third party scripts have on our potential and existing customers.

Sites like thirdpartyweb.today give some insight into the impact that ads, analytics and other third party libraries have on the Web at large:

thirdpartyweb.today by Patrick Hulce visualises the performance costs of ads and tracking scripts.

Testing without ads establishes a performance baseline.


There is often tension between developers, marketing departments and project managers when it comes to third party scripts:

The best way of circumventing fear and anxiety around third party script performance is to capture metrics that clearly articulate their performance impact.

Testing pages without ads using Calibre’s ad blocking allow you to establish a performance baseline without code changes.

Turning ad blocking on

Ad blocking can be enabled on any Test Profile by navigating to Site → Settings → Test Profiles or by using version 2.0.0+ of our command line client (CLI) or Node.js API.

Ad blocking in action

After Calibre has tested your site, stats will be shown alongside existing Test Profiles:

Total page weight without ads

Single page tests

Ad blocking is also available for single page tests via CLI. Here's a sample test:

When testing theverge.com without ads, we saw a 50% reduction in total data transferred.

How do you decide whether to use third party scripts?

We’re interested in hearing how your organisation plans for and works with third party scripts when it comes to performance and SEO.

If you have any feedback on ad blocking or new ideas that you’d like to share, please contact our team. We’d love to hear from you!

Profile photo of Ben Schwarz

Ben Schwarz

Ben is the founder of Calibre. He regularly speaks at conferences worldwide and has been involved in far reaching open source projects as well as web standards. Find him on Twitter or LinkedIn.

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