Self-moderation utility

Block someone on Substack by handle.

By @umguec·substack.com/@umguec

Drag the button below to your bookmarks bar. Then, on any substack.com page, click it, type a handle, and block—using your own logged-in session.

01 / INSTALL

Drag this to your bookmarks bar

|| Block on Substack drag me up to ⌘⇧B bar

To add it manually: make a new bookmark, name it anything, and paste the copied code as the URL.

02 / USE

On substack.com, click the bookmark

  1. Open any substack.com page while logged in.
  2. Click the Block on Substack bookmark. A panel appears top-right.
  3. Type the handle (no @) and hit Block. It resolves the handle, blocks, and confirms.

03 / PREVIEW

This is the panel you'll get

Preview—simulated, no real requests
Block a Substack user ✕
Why it has to be a bookmarklet. A site on its own domain can't block for you—the API needs your substack.com cookie, and browsers only attach that cookie to requests coming from a substack.com page. The bookmarklet runs inside that page, so your session comes along automatically. No password, token, or cookie is ever typed or stored.
If a block returns 403. Run it from a real substack.com page (your feed or a profile), not a blank tab — the request needs the page's origin to be accepted. These are Substack's own internal endpoints, so they can change without notice.