How is this different from…?
Short answers for people who already know the landscape. None of these systems is bad; most solve a different problem. Souspli borrows from several of them and says so.
The one-line version: other systems move messages between servers or peers and leave rendering to an app. Souspli moves a complete, signed, self-rendering document and makes the app incapable of leaking. The unit is the document, not the feed.
Email with PGP, or a signed PDF
The closest relatives, and the honest comparison.
- A signed PDF is attributable and self-contained. It is not interactive without JavaScript that readers rightly disable, it cannot be replied to in a structured way, and its viewer is free to fetch remote content.
- HTML email is interactive-ish, and that is exactly the problem: remote images and tracking pixels are how a newsletter learns that you opened it, when, and where. Mail clients fight this with heuristics.
- PGP signs a message body. It does not bind the program that renders it to the content, so two clients may show two people different things from the same signed bytes.
Souspli's signature covers the rendering program, the arguments and every attachment as one unit, and the container the letter runs in has no network at four independent layers. Tracking is not discouraged; it is not possible.
Nostr
Souspli uses Nostr relays as one of its transports, and every Souspli identity already has a Nostr key. The differences:
- A Nostr event is a small JSON note that each client renders as it sees fit. A letter carries its own presentation and behaviour, identical for every reader.
- Nostr content generally lives on relays and is fetched on demand, and clients load remote media by URL. A letter is complete when it arrives; nothing is fetched to show it.
- In Souspli a relay is reach, never authority: whatever a relay sends passes the same admission gate as a file from a stranger, and authorship comes only from the signature inside the letter, never from who posted it.
See the relay event.
Mastodon / ActivityPub, Bluesky / AT Protocol
These decentralise who runs the server. There is still a server: your account lives on an instance or a PDS, its operator holds the system of record, sets the visibility rules, and can see your activity. Moving is possible; custody is still someone else's.
Souspli has no accounts and no home server. Your identity is a key on your machine, your data is the letters in your library, and a forum is a set of letters that reference each other — not a place anyone hosts.
IPFS, BitTorrent, Hypercore
Content-addressed transport and storage. Souspli agrees with all of it — letters are content-addressed, and BitTorrent is one of the ways they travel. What those systems do not define is what the content is, who signed it, or how to open untrusted interactive content without it reporting on you. A web page on IPFS is still a web page: it can load anything from anywhere once it runs.
Secure Scuttlebutt
The nearest in spirit: offline-first, identity is a key, social trust instead of global reputation. SSB replicates append-only feeds — to follow someone is to replicate their log, and applications interpret messages from it. Souspli's unit is the single document, which can be handed over by any channel — a file, a paste, a QR code, a relay, a torrent — without subscribing to anybody's history. Souspli's vouches and depth-2 "tribe" owe a clear debt to SSB's hops.
Signal, Matrix
Private messaging. Excellent at confidential conversation between known parties, and not trying to be anything else. A Signal message is not a durable, portable, independently verifiable artefact you can hand to a third party as evidence of what was said; that is a feature for messaging and the opposite of what a contract, an invoice or a published article needs.
"Isn't this just a browser with the network turned off?"
Partly — deliberately. The rendering engine is Chromium, because HTML/CSS/JS is the most widely understood document technology there is. What is added:
- a format that binds program + content + attachments under one signature;
- an admission gate that verifies all of it before a byte is rendered;
- a container that removes the network, storage, navigation and every ambient capability, proven by an escape-attempt suite;
- trusted chrome the document cannot draw over, where author, signature status and every confirmation live;
- a library that indexes what you hold and the relations between letters.
What Souspli is not good at
- Real-time anything. There is no presence, typing indicator or live cursor.
- Huge public feeds. Discovery is deliberately social and local; there is no global index and no algorithmic timeline.
- Revocation. A signed letter cannot be unsaid. A seal is confidentiality against non-recipients, not access control: any recipient can forward it.
- Being finished. It is an alpha. What is missing today is listed plainly.