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Day 9: Dealing with tracking/ad blockers
4 min read

Day 9: Dealing with tracking/ad blockers

When comparing the Prezly sales pipeline Hubspot data against what I was seeing in Mixpanel there was a 10% difference. We could work with a 10% difference for most of the marketing decisions but at the same time could not use Mixpanel only for all marketing/sales reporting.

For one given period we found about 556 demos in Hubspot and only 485 in Segment/Mixpanel.

The website is setup that our forms (the form at and any other form on the website submits data directly to Hubspot Forms API urls.

This is some of the code that submits the data from the browser to hubspot:

            method: 'POST',
            headers: {
                Accept: 'application/json',
                'Content-Type': 'application/json;charset=utf-8',
            body: dataForHubspot,
            .then((response) => {
                if (response.ok) {
                    this.form.reset(); // clear input

                } else {
                    // general validation error
                    response.json().then((responsePayload) => {
                        const errors = responsePayload.errors || [];
                        if (responseContainsInvalidEmailError(errors)) {
            .catch(() => {
            .finally(() => {


Investigate how different the data is

To investigate I exported all the Hubspot demos and all the identify() calls from Day 2 (stored in DynamoDB) for a given period in a google sheet.

The first thing I did is removed the duplicates from the Hubspot list using a sheet addon:

Considering that Hubspot had the most data I added two columns to figure out if the same data was in segment. I ended up using vlookup in the 2nd table to see if the same email was there.

=iferror(vlookup(C2,'demo_request segment'!$A:$A,1,FALSE),"failed")

Added another helper column that used that data to put 0/1 in a new column


Ended up with something like this:

See lookup. Failed is data not in segment but Hubspot only

Allright. Something is up here. Comparing from both sides I found that all segment identify() data is in Hubspot but not the other way around.

Next questions for me was to figure out if this was a temporary thing? Like at one point some integration was broken/JS errors? So made a quick chart to see the distribution of misses over time:

Consistent 0-3 per day misses for this specific event 😱

This was consistent with the numbers higher up. Around 10-12% of demos end up in Hubspot but not in segment.

Ad/Tracking Blockers

Now I was pretty confident that some visitors block calls to or other integrations. The 10% rate is consistent an article I found

How Many Users Block Google Analytics, Measured in Google Analytics - Quantable
December 2017 update (blocking levels down some). June 2016 update (blocking levels a little higher). There’s now a significant number of users that use ad-blockers, estimated at about 15% in the US (according to PageFair), and that number grew quickly in 2015. Extensions like AdBlock Plus, NoScript…

I already knew that browsers are getting smarter about blocking 3th party scripts and tracking snippets. Big user of Brave myself, try to fall back to Firefox when that doesn't work, but I find myself disabling Brave shield a lot because some sites just don't work without it.

One site where it should work :-)

Reading up on the subject I discovered that a lot has happened in this area and blockers are getting better and stronger. Good. Here is a list of stuff that can potentially break my integration:

  • black lists: most hosted analytics solutions are in some kind of black list used by blocking extensions (Ghostery, uBlock Origin) or browsers itself (Firefox, Brave,..) blocking either the snippet (CDN host) or the tracking endpoint (API)
  • filename based blocks: not allowing javascripts they know are tracking snippets (analytics.js, ga.js,...)
  • 3th party cookies: Browsers making it stricter to use third party cookies

What can we do?

I'm not looking to track adblocking users or violate anyone's trust. What I am trying to get at is event-tracking for attribution purposes (marketing efforts) and if that is possible with an all-in-one segment approach.

After reading through segment forums, some docs and best practices I think we should change our segment setup:

  • ✅ Use server side tracking where we can. Not loading, Hubspot, Mixpanel or other snippets if we can offload that work to Segments server side (cloud mode) integrations
  • ✅ Serve the analytics bundle ourselves. So not but or something
  • ✅ Not use any third party cookies and make sure that cookie domain of all our tracking calls is secure and locked to (and not Wrote about this here.
  • Proxy tracking calls through our own host. So instead of the segment snippet sending it's payload to it could go to  Good thing Segment supports just which they call Custom Domain Proxy.

I did most of the things above. Still working with Segment and our website infrastructure to also proxy the tracking calls.

Tomorrow I will try to discover if I can back fill the missing data in any way.