When Curation Sync is on, Spine stores your metadata corrections as tags on your own Torbox downloads. They look like gibberish. They aren't — and you shouldn't have to take our word for it. Paste one here and watch it decode, step by step, on your own machine.
Nothing you paste leaves this page. There is no upload and no server.
This page sends a Content-Security-Policy of default-src 'none', which means
your browser refuses to let it make a network request at all. Turn off your Wi-Fi and
reload — it still works.
Read the code that just ran: decode.js · app.js · its tests · test fixtures
The tag carries eleven possible fields, all listed above when you decode one. Everything below is absent by construction — there is no field for it, so there is nothing to omit, redact, or trust us about.
The one field that touches your files is the book key, and it is a hash: the first 8 bytes of SHA-256 over the book's path inside the download. Your other device recognises a book by hashing its own paths and looking for a match. Eight bytes cannot be turned back into a filename.
Torbox rewrites tags — it lowercases every character and silently strips :,
/ and ". That rules out storing readable text (your book titles
would come back mangled) and rules out base64 (lowercasing corrupts it). So Spine writes
the corrections as JSON with one-letter keys, compresses it, and encodes the result in
base32, whose alphabet survives lowercasing byte for byte. The result is sliced into
110-character pieces because Torbox rejects a tag much longer than that, and each piece
carries its own position so the order Torbox returns them in doesn't matter.
None of this is encryption. There is no key and no secret. It's compression and encoding, chosen to survive a sanitiser — which is exactly why this page can decode your tag without you giving it anything.
Sign in at torbox.app, open your downloads, and find the download an audiobook came from. Its tags are listed on the download; copy all of them. In Spine, the same feature lives at Settings → Torbox → Curation Sync, where it's off unless you turned it on.