tagdrop

TagDrop turns small files — text, HTML pages, images, audio, SVGs — into self-contained QR codes that work completely offline. Print one on a sticker or sheet of paper and leave it somewhere; anyone with the TagDrop app (or any QR scanner that follows tagdrop: links) can scan it and view the content immediately, with no internet connection, server, or account required. Think of it as a digital geocache: instead of a logbook in a box, the "cache" is the QR code itself. What you can do with it

• Drop a single page — encode text, an HTML page, an SVG image, or JSON into one QR code, either in-app (Create Cache) or with the web generator.
• Drop a whole "paper" — a printable sheet with a directory QR code (a paper manifest) plus one QR per file, built in-app (Create Paper) or with the web generator. Pages can link to each other with ordinary relative links, so a small static site survives being printed and scanned back in.
• Spread large content across multiple codes — split a payload too big for one QR into multiple sector codes placed along a trail. The app collects sectors in any order, reassembles and verifies them, and can recover a single missing sector from an optional parity code.
• Build trails, collections, and replies — link papers together with location hints, tag a loose set of stickers with a shared collection so they group into one card on the home screen and map, or mark a code as a reply to another to thread a conversation across drops.
• Browse offline — scanned pages render in an in-app viewer, with search and #hashtag filtering, and a hex/CBOR inspector for the curious. The Collections, History, and Map tabs let you revisit, locate, and manage everything you've found, and a single file can back up or restore it all.
• Tap instead of scan — write any TagDrop code to a blank or rewritable NFC tag, then read it back with a tap instead of the camera.
• Sign your drops — post-quantum (ML-DSA-44) Verified Authorship signing lets anyone who scans your codes recognise them as genuinely yours after the first scan (trust-on-first-use), with a ✅/⚠️/🔏 badge shown on every signed item. Back up your signing identity to a passphrase-protected file to keep the same recognisable signer across devices.

- Wire format: QDEF redefined Split's group_id as an opaque grouping token rather than a verified hash. This app adds its own payload_hash field to keep the same reassembly-integrity check (SPEC.md version 18). Multi-code QR/NFC drops (content or paper spanning more than one code) made before this update won't reassemble correctly, and vice versa — regenerate and reprint/rewrite any of those after updating. Single-code drops are unaffected.
- Security: a scanned file's declared name is now rejec