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What is this?

This is a small script that goes through the list of your Substack email subscribers and creates a distribution table for the domain names.

• ☑️ No dependency. Uses Node's native CVS parser
• ☑️ Easy to audit: just one file
• ☑️ Works directly from the command line. No need to clone the repo.

Why does this exist?

This helps get an understanding of where your subcribers are. The interesting data is in the long tail of 1-2 subs from domains like amazon.com or microsoft.com.

In the age of AI, do we really need a script like this? I'd argue yes for 2 reasons:

1. Subscriber email address is PII (personally identifiable information) and they'll be thankful if this info isn't shared with some cloud AI provider

2. Using AI for such a simple task is like using a machine gun to kill a mosquito! This script can handle millions of records because it only processes one line at a time.

Since the output is scraped from PII, you can feed it to AI. As a bonus, the output of this script burns much less tokens because it aggregates multiple users from the same domain.

How to use it?

You need to have Node.js installed.

Go to Substack Dasbhboard and export all subscribers then run the following command:

npx -format table substack-email-distribution path/to/file.csv

npx is part of Node.js which is available out of the box.

Tip: the result can be quite long. You may want to forward the output to a file by appending this to your command: > myfile.txt

You can also specify a format with --format or -f which can be:

• table: (default)
• json: json object where key is the email domain and value is the frequency of that domain
• csv: comma separated values (for for spreadsheets, but if you're proficient in spreadsheets you probably don't need this script!)
• tsv: tab separated values (good for bash processing)

The full list of options can be seen using -h option.

--format table:

┌───────────────────────────────────┬───────┐
│ (index)                           │ Count │
├───────────────────────────────────┼───────┤
│ gmail.com                         │ 13069 │
│ hotmail.com                       │ 335   │
│ yahoo.com                         │ 268   │
│ outlook.com                       │ 221   │
│ icloud.com                        │ 209   │
...

--format json:

{
  "gmail.com": 13069,
  "hotmail.com": 335,
  "yahoo.com": 268,
  "outlook.com": 221,
  "icloud.com": 209,
  ...

--format csv:

gmail.com,13069
hotmail.com,335
yahoo.com,268
outlook.com,221
icloud.com,209
...

--format tsv:

gmail.com	13069
hotmail.com	335
yahoo.com	268
outlook.com	221
icloud.com	209
...

Requirement

Node v24+.