On Substack, open rate means the percentage of recipients who opened your email/newsletter. It’s a basic email performance metric, so if 100 people receive a post and 40 open it, the open rate is 40%.

What it tells you

Open rate gives you a quick sense of how well your subject line, sender name, and audience interest are working. A higher number usually suggests people are noticing and opening your posts, while a lower number can mean the topic, timing, or audience fit needs work.

What to know

  • It counts openers , not just total opens, so one person opening the same email multiple times does not always raise the percentage the same way.
  • It is not perfectly accurate because privacy features and image loading can make opens look higher or less reliable than actual human reads.
  • On Substack, it is best used as one signal, not the only measure of success; clicks, replies, and paid conversions matter too.

Simple example

If your Substack post goes to 500 subscribers and 150 of them open it, your open rate is 30%. That does not mean 30% read every word, only that they opened the email or post notification.

TL;DR

Open rate on Substack is the share of subscribers who open your email, and it helps you gauge initial interest — but it is only an approximate measure of engagement.