Privacy policy
Last updated 2026-10-28.
How to use Substack ("we", "the app") helps writers schedule Substack Notes and LinkedIn posts, see their Substack analytics, and turn their own articles into Notes written in their voice. This page explains what we collect, why, where it is kept, who processes it, and how to remove it. The short version: we hold only what the app needs to do what you ask, we do not sell or share it for advertising, and you can delete all of it yourself at any time.
Who is responsible
The app is operated by Lily Ventures, 524 Broadway, New York, NY 10012, USA, which is responsible for your data (the "controller"). Questions, requests and complaints: privacy@howtousesubstack.com.
What we collect
| Data | Where it comes from | Why |
|---|---|---|
| Your email address and the name we invited you with | Your invitation and sign-in | To let you sign in (we email you a one-time code) and to contact you about your account |
Your Substack session (the substack.sid cookie), your Substack user id, handle, name and the newsletters you run | Our browser extension, when you connect Substack | To read your stats and to publish, schedule and delete Notes you ask for |
| Your LinkedIn access token, member id, name and profile picture link | LinkedIn, when you connect it | To publish, schedule and delete LinkedIn posts you ask for |
| Your newsletters' statistics: per-post views, opens, clicks, shares, restacks, reactions, comment counts, subscribers gained and lost; daily subscriber totals; your Notes and their engagement | Substack, using your session | To show your analytics |
| Your own published writing: your Notes and articles on Substack, and posts you paste in by hand | Substack, using your session; you | To learn your voice and suggest Notes that sound like you (see "AI services" below) |
| Posts you write, generate or schedule here: text, links and images | You, and the suggestions you keep or edit | To publish them when and where you ask, and to improve the suggestions |
| A log of what the app did for you (connected, collected, published, cancelled) | The app | So you and we can see what happened |
| Which browsers run the extension, as a coarse label such as "Chrome on macOS" | Your browser, when it connects | So you can see and revoke them |
| The approximate region your browser connected from (for example "Western Europe"), never your address or exact location | Your connection | Technical: where to run calls to Substack |
| Request and error logs, without cookies, tokens or post content | The app | To keep the service working and secure |
Your readers. Some Substack statistics responses include lists of individual readers (for example who liked a post). We remove those lists before anything is stored. We keep counts, never your subscribers' names or email addresses.
What we do with your accounts
- We publish, schedule or delete posts only when you ask us to, on the accounts you choose. Nothing is posted automatically.
- We read your Substack statistics regularly (about every six hours while your browser is open) to keep your analytics current, and we read your own published Notes to build your voice profile.
- Once a day we make read-only calls to Substack with your session to check that the parts of Substack we rely on still work as expected. These calls change nothing.
- We never read or send your Substack or LinkedIn messages, and we never change your account settings.
The browser extension
The extension reads one thing: your Substack session cookie on substack.com. It sends it only to this app, when you connect and whenever Substack renews it, and it asks the app to refresh your statistics about once an hour while your browser is open. It does not read your browsing history, the pages you visit, or anything on other websites.
AI services
When you ask for Notes from an article, we send that article, a sample of your own published writing and the Notes you kept or edited before to Anthropic (the Claude models), which writes the suggestions, and short passages of your writing to OpenAI, which turns them into numbers we use to pick the best examples of your voice. Both run through Cloudflare's AI Gateway, which we have set not to keep the content. Under Anthropic's and OpenAI's business terms, what we send is not used to train their models. When the weekly growth report ships, it will send your own aggregate statistics to Anthropic in the same way. We do not train models on your data ourselves.
What we do not do
- We do not sell your data or share it with advertisers or data brokers.
- We use no advertising or analytics trackers. The only cookie this site sets is our own sign-in cookie, which keeps you signed in for 30 days.
- We do not show your data to other writers. Each writer sees only their own.
Who else processes it
- Cloudflare hosts the app, its database and stored files, and sends our emails (the sign-in code, and later reminders and reports). The database and files are kept in Cloudflare's Western Europe region.
- Anthropic and OpenAI, as described under "AI services".
- Substack and LinkedIn receive the requests we make on your behalf, under their own privacy policies.
No one else receives your data. If that changes, for example a service that relays calls to Substack, we will update this policy first.
Support access
To help you, an administrator of the app can open your pages in a read-only view and see what you see. They cannot publish, delete or connect anything as you, and every such view is recorded in the administrator's own activity log.
How we protect it
Substack sessions and LinkedIn tokens are encrypted (AES-256-GCM) with a key kept separately from the database, and are decrypted only at the moment they are used. Every page except this one and the sign-in page requires sign-in, each writer can reach only their own data, and sign-in codes, session cookies, pairing codes and extension tokens are stored only as hashes. No system is perfectly secure; if we learn of a breach that affects you, we will tell you without undue delay.
How long we keep it
- While your account is open, we keep what is listed above.
- Disconnecting an account deletes its stored session or token immediately and cancels its scheduled LinkedIn posts.
- Deleting your account (Your account → Delete) erases your connected accounts, stored sessions, analytics, writing samples, posts, scheduled jobs, files, sign-in sessions and activity log. Notes waiting in Substack's scheduler are cancelled. Posts already published on Substack or LinkedIn stay there.
- Request logs are kept by Cloudflare for a few days. The database's recovery history, used only to restore it after a fault, keeps deleted data for up to 30 days before it is gone.
Your rights
You can see your connected accounts and activity on your home page, and delete everything yourself under Your account. You can also ask us for a copy of your data, to correct it, or to stop a particular use of it, by writing to privacy@howtousesubstack.com; we answer within 30 days. If you are in the EU, the UK or a similar jurisdiction, you can also complain to your data protection authority.
We process your data to provide the service you asked for (performance of a contract) and, for security and the daily read-only checks, on our legitimate interest in keeping the service safe and working.
To cut our access from the other side at any time: log out of substack.com (this ends the Substack session we hold), and remove "How to use Substack" under LinkedIn → Settings → Data privacy → Permitted services.
Children
The app is not meant for anyone under 16, and we do not knowingly hold their data.
Changes
If we change this policy in a way that matters, we will tell you in the app or by email before the change applies. The date at the top shows the latest version.