Frequently asked question

What is it?

Blockmetry is a pipeline to accurately measure content blocking rates, and, optionally, react. This includes adblocking and analytics blocking.

We work with each customer to understand their measurement needs, and produce unique code for each website to measure exactly what the customer wants. Part of this upfront work is making sure the code measures the content (ads, analytics, etc) you already use on the site instead of introducing a new, or moving to a different, ad serving network or technology.

The data reports show up in the Blockmetry analytics dashboard.

How does Blockmetry work?

Blockmetry works by analyzing just the specific HTML where an ad expected to be placed, and also the JavaScript to see if the analytics code loaded correctly. Although it is possible to fingerprint browsers and detect that some content blocking extensions are installed, Blockmetry doesn’t do that - see the specific question about this below.

Because of how Blockmetry works, it is not possible to know why an ad or analytics JavaScript did not load. It could be a content blocker, network failure, or even network-level content modification by ISPs or corporate networks. All these mean that end-users are not getting the experience publishers wish, and Blockmetry measures that.

Does Blockmetry slow down the loading of the site?

A tiny bit that users will not notice. The code is embedded inline in your HTML, and will fire only once the page is fully loaded.

This has two advantages:

The actual logging is done by calling a custom Amazon Cloudfront URL, meaning it will load extremely fast worldwide because Cloudfront is a content distribution network.

What should Blockmetry be configure to track?

A good way to think about Blockmetry measurement is content placed within a template in a site. For example, the content is a specific ad placement in an HTML template/layout. Likewise, the content could be the JavaScript of a third-party analytics package such as Google Analytics.

To take a simple example of measuring ad blocking, some useful scenarios to consider include:

Does Blockmetry use device fingerprinting?

Not at all! We hate privacy-invasive techniques and Blockmetry does not use any device or browser fingerprinting. Further, Blockmetry’s measurement code does not set or read cookies, and we ask our customers to not send user-identifying information to Blockmetry’s measurement pipeline.

Can Blockmetry itself be blocked?

The short answer is everything can be blocked. We’ve designed the system to minimize the likelihood and impact of a block rule specifically affecting your site or Blockmetry in general.

Fundamental to our design is that we create unique code for each website. This means that if the code from a site is added to a block list, only that site’s measurement is affected.

We also monitor a large number of popular block lists in order to react quickly if a rule targeting a customer site is added to a block list. This monitoring has already identified rules targeting some customer websites, allowing them to design a better user experience.

Can a site show an ad to an ad blocking user and recover revenue? Can a site react in any other way?

Yes. We can work with you to build and deploy custom code to react based on the results of the code’s measurement.

In more detail: By default, the Blockmetry code only measures content blocking rates and nothing more. We can modify the code for your website to react in various ways when it detects a content blocking visitor. Some common examples:

  1. Show a user survey to understand your audience’s motivations and concerns leading to blocking ads on your site.

  2. Show a message to, for example, promote joining a mailing list, paying for a subscription, or simply asking the user to re-enable ads for the site.

  3. Force-show an ad. As this reaction can hurt your relationship with your users even more, we can work with you to design a user-friendly fallback ad.

Data security and jurisdiction

Data security is implemented using both technical and business processes.


All measurement, communications with the databases, and reporting in web front end is over HTTPS.

The data is not currently encrypted at rest in the database; we plan to change that in the future.

Business processes

We work with each customer to decide which email account has access to the data. We use Google account logins, which means the customer has full control over who can log in. The account is usually the one used to access one of Google Analytics, Search Console, AdSense, or AdWords.

We also have a standard non-disclosure agreement we can use to protect access and disclosure to the data.

Storage location

By default, all data is stored in the USA. You can request different a data jurisdiction.

Data deletion

We can agree a process to delete log files and non-aggregate (raw) data on request.


Customers can request specific requirements or changes to some of the details mentioned above.

Bots and users with JavaScript disabled

Blockmetry measures browsers that have JavaScript disabled. Although these browsers do not load an ad, they are not considered ad blockers and are monitored in a separate metric.

Bots are filtered prior to any analysis (although they get logged). Bot filtering is an on-going process, and we have a pipeline dedicated to continuously improving bot detection.