When logged into your Substack account, head to your Posts tab and click on the down arrow next to each individual post.
Here, you'll find information on where readers of that particular post came from:
What does each traffic source mean?
Email- Your post was sent as a newsletter and opened and viewed in an email sent from your publication.
Direct- When a reader types your publication URL directly into the browser and clicks on your post or when there's an unknown source such as when a reader is using a web browser anonymously.
Other- Sources that account for <1% of views will appear as "Other".
Popular sites- If you or other readers shares your post on social media (Facebook, Twitter, etc), we'll display the site domain where readers clicked on the link and landed on your Substack post.