What the extension sends, what this server stores, and what's public by design.
While enabled, the extension sends this appview a SHA-256 hash of the current tab's normalized URL on every navigation, to check whether the page has any messages. It never sends the URL itself. For a page with no messages, nearly all of anyone's browsing, that hash matches nothing and nothing is kept.
Be clear about what this does and does not do. It is not cryptographic protection, and it does not make URLs secret: for a page that already has a message, this server stores that page's URL in plain text right alongside its hash, because the message itself is a public record. An operator willing to hash a large dictionary of known URLs could match some misses back, too. What hashing does do is stop this server from building a browsing log out of the pages that have nothing to do with Soapstone, which is most of anyone's browsing. Localhost, private IP ranges, and URLs carrying credentials or a token-like query parameter are never looked up at all.
A message you post is written to your own atproto repository, not to a database here: you authenticate directly with your own provider (PDS) over OAuth, and this server never sees your password. Records on atproto are public network data by design: your handle, the message text, and the page URL are all readable by anyone who indexes the firehose, the same way this appview does. Deleting a message from your dashboard deletes the record from your repo, which removes it everywhere.
No analytics, no ads, no third-party trackers, no data sold or shared beyond what's described above.
Privacy questions, abuse reports, or takedown requests: luiscomsnofim@gmail.com.