Substack Email Subscribers
A new series on Technology Should Be Simple discussing the technical aspects of using and working with Substack.
Learning Substack is a new series on discussing the technical aspects of using and working with Substack. Mixed with insights on how I personally use the platform. If you’re unfamiliar with Substack, it’s the platform that powers Technology Should Be Simple.
“It looks like you haven't opened our email in a long time.”
If you've ever received an email like this, it's because newsletter platforms like Substack track engagement metrics—including whether or not you open their emails.
I can’t count how many times I’ve received an email like this, and this post is going to dive into the mechanics of emails and what these metrics are really tracking.
What is being tracked
Let’s start with the Subscriber page in your Substack Dashboard.
The subscribers page is your newsletter contact list. Here is everyone that subscribes to your newsletter. If anyone has given you their email address, they end up here.
Substack tracks various metrics on these email addresses. The primary metrics (and the default ones shown) are:
Free vs Paid Subscriber - Self explanatory, but this shows you if the email address is a free subscriber or a paid member of your newsletter.
Activity - This is a 5 star rating system developed by Substack to share “a high-level rating of how actively the subscriber has used your newsletter in the last month, including email opens and web views.”
Subscription Date - This is date the email address was first added to your newsletter subscription. The first time it entered your contact list.
Emails Opened - This tracks how many emails were opened in the inbox of this email address.
Links Clicked - How many times this email address clicked a link when they opened your newsletter in their inbox.
Subscription Source - What brought this email address to your newsletter.
If you click the Columns button on the subscriber page, you will see many other data points being track that let you really refine and drill down your audience. But I’m going to focus on these primary ones.
How it works
So how is Substack actually collecting this information? How does it know when someone has opened an email or click a link?
For email opens and reading in an inbox, Substack is using a tracking pixel in images.
A tracking pixel is a tiny, invisible image (usually 1x1 pixel) embedded in the email. When the recipient opens the email, the image is loaded from Substacks server, allowing them to track that the email was opened.
Substack uses tracking pixels in its newsletters to measure open rates. When a subscriber opens a Substack email, the pixel loads, and Substack records the open.
For link clicks, Substack is using a tracking system that creates unique URLs for each email address the newsletter is sent to.
When a subscriber clicks a link in an email, they are briefly sent through a Substack URL that records the click before forwarding them to the intended webpage. Either your newsletter or an outside link.
This allows Substack to track which links are being clicked, how often, and by whom.
Substack used both of these methods to understand who is reading your newsletter and where they are going once they’ve read it. This data is shared in your Subscriber page and used to create the Activity 5-Star metric.
Limitations to know
Tracking pixels and link click tracking in email newsletters come with significant limitations, due to privacy settings and different email clients. Most modern email clients, now preload or block tracking pixels to protect user privacy. This means an email may appear as "opened" even if the recipient never actually viewed it, or it may not register at all if the recipient's email client blocks the pixel. As a result, open rates can become an unreliable metric.
Similarly, link click tracking is affected by browser privacy settings, VPNs, and ad blockers, which can strip tracking parameters or prevent redirections. Some users may also copy and paste links directly into their browser instead of clicking them, bypassing Substack’s tracking entirely.
Which get me to my opening line, “It looks like you haven't opened our email in a long time.” I use an email service that blocks tracking entirely, and I’m not alone in this. If I’m subscribed to a newsletter, I show up as a 1 or 0 star rating in Substack’s Activity. I’m shows as 0 star subscriber to my own newsletter.
I open most newsletters I’m subscribed to, but my email client prevents that data from ever getting back to the sender. So your subscriber list may show low open rates, but that might not be the whole story. Particularly you cater to a more tech savvy or privacy focused audience.
There is an additional feature now showing up in email clients that allow the use of one time or temporary email addresses. These are the subscribers you have that have an email address of random numbers and letters. This is a further privacy measure by some users to protect themselves from tracking.
I have seen several guides o newsletters talking about purging their subscriber lists. Deleting emails that are not showing any engagement. The way this engagement is tracked in not always reliable, as explained above.
What to focus on
So what metrics can I rely on for my newsletter? I’m not saying to throw out the metrics provided on your subscriber page, but take them with a grain of salt. There are many ways they can be distorted.
Focus on actual subscriber growth, how many people are subscribing to your newsletter.
If you have a paid their of your newsletter, focus on the conversation of free to paid subscribers.
These are much more stick stats that can’t be skewed by privacy settings. Open rates are a useful reference, but they shouldn't dictate your entire strategy. Quality content and direct reader engagement matter far more than a number in your dashboard.
Additional Resources
Substack has some great articles in their support section that goes into more detail of how to use your dashboard and the metrics provides.
I highly recommend reading through these articles to understand how to use the Substack platform you are publishing on.
Substack’s analytics can be helpful, but they have limitations. If you're a writer, use these tools wisely. Understand what they can and can’t tell you. And if you're a subscriber, know that your email activity might not be as private as you think.
Have you looked at your Substack metrics? How much do you rely on them? Let’s discuss in the comments!