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Substack Notes

Free tier: Substack Notes is free to use. No API subscription required.

Substack Notes posts immediately -- there is no scheduling API. Posts sent via this provider go out at the moment you approve them.

1. What Postlane uses it for​

Postlane uses your Substack session cookie to post directly to Substack Notes. This is the same mechanism your browser uses when you are logged in to Substack -- there is no official API.

Because this uses a browser session cookie and not a stable API key, it is less reliable than other providers. The cookie expires when you sign out of Substack and must be re-entered. If reliability matters, use Substack Notes as a secondary provider alongside a more stable one.

2. Pricing​

None. Posting to Substack Notes is free.

3. Limitations​

  • Immediate posting only -- posts go out when approved, not at a scheduled time
  • No delete via API -- Postlane cannot delete a Substack Note after it is posted
  • No fallback chain support for scheduled posts -- because Notes posts immediately, it cannot participate in time-based fallback chains
  • Cookie expires on sign-out -- you must re-enter the cookie every time you sign out of Substack

You need the substack.sid cookie from a browser where you are signed in to Substack.

Chrome or Edge​

  1. Go to substack.com and sign in if you are not already
  2. Press F12 to open DevTools
  3. Click the Application tab
  4. In the left panel, expand Cookies and click https://substack.com
  5. Find the row where the Name column shows substack.sid
  6. Click that row and copy the full value from the Value column

Firefox​

  1. Go to substack.com and sign in if you are not already
  2. Press F12 to open DevTools
  3. Click the Storage tab
  4. In the left panel, expand Cookies and click https://substack.com
  5. Find the row where the Name column shows substack.sid
  6. Copy the full value from the Value column

Safari​

  1. Go to substack.com and sign in if you are not already
  2. Open Develop → Show Web Inspector (enable the Develop menu first in Safari → Settings → Advanced → Show features for web developers)
  3. Click the Storage tab
  4. In the left panel, click Cookies → substack.com
  5. Find substack.sid and copy its value

The cookie value is a long string starting with s%3A or similar. Copy the entire value.

  1. Open the Postlane desktop app and go to Settings → Scheduler
  2. Click Add provider and select Substack Notes
  3. Paste the full cookie value into the text area
  4. Click Save
Session expiry

This cookie expires when you sign out of Substack. If Substack Notes posts start failing, sign back in to Substack and repeat the steps above to get a fresh cookie.

6. Per-repo override​

To use Substack Notes for only specific repositories:

  1. Go to Settings → Repos and click the repository name
  2. Click Configure → Scheduler
  3. Select Substack Notes and paste the cookie
  4. Click Save

7. Troubleshooting​

Posts are failing with an authentication error

Your session cookie has expired. Sign back in to Substack, extract a fresh substack.sid cookie following the steps above, and re-enter it in Settings.

Still signed in to Substack but posts are failing

Substack may have rotated your session. Sign out of Substack completely, sign back in, then extract a fresh cookie.