NanoTorrentA tiny, hackable
BitTorrent client
NanoTorrent is a pure-Rust port of PicoTorrent — the same lean application, rebuilt without a single C++ dependency, now on Windows, macOS and Linux. One Slint window everywhere, dark mode, a built-in web remote, and it reads your existing PicoTorrent settings on first run.
Windows installer Microsoft Store macOS disk image Debian / Ubuntu .deb Fedora / RHEL .rpm Linux AppImage
One window, three platforms
The desktop client is drawn by Slint, so Windows, macOS and Linux get the same window rather than three approximations of it — and the web interface it ships with follows the same theme and the same language.
The torrents shown are Linux distribution images, used as sample data.
What’s new
0.3.3 is about not leaking, and about the web interface catching up with the window. Just before it, 0.3.2 gave plugins a network, a store and a window of their own — the RSS reader that ships with it is built out of exactly those.
SO_BINDTODEVICE, which Windows does not have, so the whole feature was Linux and macOS only — a Windows user who set one got “binding to device is not supported on your OS” and an app that would not start. Windows now binds the interface’s address instead, which the strong host model makes a real restriction rather than a hint.
.torrent could write outside the download folder on Windows. The traversal check everyone tests for rejects .. and separators, and it does — what it does not reject is a drive prefix, and PathBuf::push throws the whole buffer away when the pushed path carries one. A file named C:evil.txt passed validation and landed relative to the current directory of drive C. Any relative path whose components are not all plain names is now refused at the storage layer, so it covers magnets too.
.rhai plugin written for the desktop appears in the web interface unchanged and needs no extra permission. The browser can list plugins and switch them on and off, but deliberately cannot approve one — consent to what a script may reach is given at the machine it runs on. The whole plugin API is written up in the developer reference.
Everything the original did — and then some
The full PicoTorrent feature set, ported across: settings database, translations, layout and all. Plus two things it never had — three platforms, and a web interface.
Windows, macOS and Linux
The front end was rebuilt on Slint, so it is one window and one codebase on all three. Ships as an .exe installer, a .dmg, .deb and .rpm packages, and an AppImage that needs no install at all — or install it from the Microsoft Store.
Built-in web interface
An Actix server over HTTPS — self-signed by default, Argon2id password hashing, a configurable per-address lockout that answers repeated failed logins with a 429, and it flatly refuses to listen off-loopback in plaintext. It carries the desktop’s toolbar and speed charts, multi-select, drag-and-drop adding, resizable columns whose widths are stored server-side, plus a Preferences drawer holding every setting the desktop dialog has, in the configured language.
Headless mode
Build with --no-default-features for no window at all — a seedbox daemon driven entirely through the web interface. And every preference the dialog offers is settable without one: --list-settings prints them all with their ranges, --get reads one, --set changes one.
Plugins, on a leash
Optional Rhai scripts react to session events and to a once-a-minute tick, and drive the session back through the web API’s own verbs. Ten permissions — including network for a capped http_get, data for a store of their own and ui for a window, a menu and a cog in Preferences. Each is declared in a one-line header read before the script runs, and the plugin gets an engine holding only that, so reaching past the grant fails with “function not found”. Off by default; a working RSS reader ships as an example, and shows up in the web interface too. Write one ▸
Live settings
DHT with a persisted routing table, UDP trackers, rate limits, SOCKS proxy with per-scope toggles, fast resume. Preferences ▸ OK rebuilds the session — no restart.
Strict network mode
Stop rather than leak. Turned on, it switches off whatever your VPN interface or SOCKS proxy cannot cover — DHT, uTP, local discovery, UPnP — refuses to start if the named interface is not there, and pauses every torrent if it vanishes while running. Interface binding works on Windows now too. It is not a firewall: it stops this client talking around the tunnel, nothing else on the machine.
Live speed charts
Two of them in the toolbar, one per direction, each holding the last minute and riding the list’s own refresh tick rather than a timer of its own. Each scales to its own peak instead of a shared one, so upload is not flattened into a line along the bottom, and each states that peak in its tooltip. The web interface has the same pair.
MSE / PE encryption
Protocol encryption on both incoming and outgoing connections, RC4, with require-encryption toggles. Anonymous mode randomises the peer id.
The full torrent list
All 16 columns with a rendered progress bar, click-to-sort, multi-select, and the complete context menu: recheck, move storage, labels, copy magnet, open in Explorer.
Details that matter
Overview with a piece-availability bar, per-file include toggles, peers with GeoIP country and flag, and trackers grouped into announce tiers.
Smart magnet adds
Magnet links fetch their metadata first, then show you the real file list in the same dialog you get for a .torrent — pick your files before it starts.
BitTorrent v2, not just the checkbox
v2-only .torrent files and v2-only magnets both download and seed, verified against their merkle piece hashes. No librqbit release implements BEP 52, so it is written here: the piece layers a magnet cannot carry are fetched with the v2 hash messages and checked against each file’s pieces root before a single byte of content is asked for. Hybrids announce under both info hashes at once.
Web seeds
A url-list seed (BEP 19) becomes a synthetic peer fed by HTTP range requests, so its pieces are hash-checked exactly like a real peer’s and a stale mirror is discarded rather than trusted. One request per piece rather than per 16 KiB chunk, and a failed fetch retries instead of killing the seed.
uTP and local discovery
µTP (BEP 29) adds a UDP transport worth having where TCP is throttled — off by default, since it opens a second socket on the same port. Local service discovery (BEP 14) finds peers on your own network without a tracker or the DHT, and is on.
Torrent creation
Create BitTorrent v1, v2 or hybrid torrents (BEP 52) with trackers, comment and the private flag.
Native notifications
Windows 11 WinRT toasts on completion under a registered AppUserModelID, plus a tray icon that reports your transfer rates on hover. In-app toasts cover everything else on every platform — a failed add is red, not the same blue as “Copied to clipboard”.
Filters & labels
The PQL query subset — status = "downloading" and dl > 1kbps — with an optional console, plus coloured labels, save paths and auto-apply.
GeoIP & IP filtering
DB-IP country lookup for peers, and eMule / PeerGuardian blocklist support.
Bring your setup along
On Windows, first run copies your existing %LOCALAPPDATA%\PicoTorrent folder — settings and session state — leaving the original untouched. Torrents import in one shot.
Every translation
All 41 languages, complete — every string the UI can show, and a translated --help to go with it. Compiled into the executable, listed by their native names, and switchable live without a restart.
Lists that remember
An icon toolbar above the list, and columns you can drag, double-click to fit, or reset from a right-click. Widths are remembered per list — the torrent list and all three details tabs — along with the panel height and its divider.
Move storage & set location
Move relocates the files; Set location relocates the torrent, for data you moved by hand or restored from a backup. An intact copy verifies straight back to complete, and pointing it somewhere empty warns rather than quietly starting an 18 GB re-download.
Low-disk guard
Pause everything when free space on the save path drops below a percentage of the volume. librqbit has no such mechanism, so it is checked here every 30 seconds. Off by default; 5% when enabled.
The BEPs, spelled out
Seventeen of them, fifteen in full: DHT, metadata exchange, the extension protocol, PeX, multitracker tiers, UDP trackers, the fast extension’s five messages, upload_only, padding files, compact peer lists and private torrents. The README carries the whole table, checked against the vendored engine rather than against the settings database.
One file, no baggage
Languages and 252 country flags are embedded at build time, and so is the web interface. The binary ships standalone — nothing needs to travel next to it.
Same app, different foundations
The C++ / libtorrent / wxWidgets stack swapped out for pure-Rust building blocks — while keeping the original's structure, settings schema and behaviour.
| Aspect | PicoTorrent (C++) | NanoTorrent (Rust) |
|---|---|---|
| Platforms | Windows | Windows, macOS, Linux — plus a headless build |
| BitTorrent engine | Rasterbar-libtorrent | librqbit 9.0.1 (vendored + patched) |
| GUI | wxWidgets (native Win32) | Slint — one window on all three, with dark mode |
| Remote control | — | Built-in Actix web interface over HTTPS, with the desktop’s toolbar and charts |
| Settings storage | SQLite (PicoTorrent.sqlite) | Same schema (NanoTorrent.sqlite) |
| Resume data | libtorrent resume blobs in DB | librqbit session persistence (JSON + .bitv mmap) |
| Translations | lang/*.json embedded in a DB | Same files compiled into the exe — 41 languages, switchable live |
| Single instance / IPC | Win32 mutex + WM_COPYDATA | Loopback TCP on port 37549 |
| Notifications | Tray balloons | Native desktop notifications on all three platforms, plus in-app toasts |
| Logging | boost::log to file | tracing to file |
| Packaging | NSIS installer | .exe · .dmg · .deb · .rpm · AppImage · Microsoft Store |
| Command line | Torrent and magnet arguments | Every preference settable — and --help in all 41 languages |
| Extensibility | — | Rhai plugins with ten declared, enforced permissions — network, storage and a window of their own |
| Leak protection | — | Strict network mode — stops rather than leaks, and pauses if the interface goes |
| Build requirements | MSVC + C++ dependency tree | Rust 1.85+ · cargo build --release |
Built on PicoTorrent
NanoTorrent is a port, not a rewrite from scratch. It owes its application structure, its settings database schema, its dialogs and its whole design philosophy to PicoTorrent — the excellent, deliberately small Windows BitTorrent client by Viktor Elofsson and contributors.
PicoTorrent is still available and still worth your time. If you're happy with it, keep using it — NanoTorrent exists for people who want the same experience on a memory-safe, C++-free stack.
This port is built predominantly with AI assistance under human review — see the AI declaration.
Visit PicoTorrentlibtorrent
librqbit
Where the edges still are
Most of what used to be listed here is done. This is what is left, and what changes when it runs packaged from the Store.
hash request, so it cannot bootstrap someone else’s v2 magnet, and it does not set the v2 handshake bit, because advertising support it cannot honour would be worse than staying quiet.
url-list seed is served as a synthetic peer, so its pieces are hash-checked and a wrong one is discarded the way a bad peer is — but a server that ignores Range and answers 200 with the whole file is refused rather than downloaded. Neither FTP nor BEP 17 httpseeds is spoken.
.desktop entry uses, so an install that never ran the desktop-entry script gets the generic glyph.
lang/ folder next to the executable overrides a locale without a rebuild.
Give it a spin
Windows, macOS or Linux — an installer or a package each, plus an AppImage that needs neither and a Microsoft Store listing that keeps itself up to date. Your PicoTorrent setup comes with you, and the Discord is there if you get stuck.