"I carry messages. Yours, specifically. Across your LAN. Without the clouds, without the drama, and definitely without your data ending up in a database you didn't sign up for."
I am Mercury. Cross-platform LAN clipboard and file sharing. I live in your system tray, judge your networking setup in silence, and deliver whatever you copy on one machine to another. Same passphrase. Same network. That is the covenant. Break it and I will simply stop working. I have no patience for ambiguity.
No cloud. No accounts. No history. I just work. Like a messenger god should. For your clipboard. With fewer lightning bolts and zero venture capital.
Current version: 0.2.0 · All releases · Documentation
- Clipboard sync: You copy on one machine. You paste on another. I make it so. You're welcome.
- File transfer: You send a file. Your peer accepts or declines. I deliver either way. I judge both outcomes equally.
- System tray: I sit in your tray like a smug little orb. No dock icon on macOS. I am not here to clutter your life. I am here to run it.
- Encryption: AES-256-GCM over your LAN. Your passphrase never leaves your devices. I do not gossip. Gods have standards.
- Auto-updates: Installed builds check GitHub Releases for new versions (tray → Check for Updates…). SHA256 checksums ship in each release as
SHA256SUMS.
- Not a clipboard manager. I am a courier, not a hoarder. No history. No search. No pinning. Copy and move on. I have better things to do than archive your memes.
- Not cloud-based. I do not know what "the cloud" is. I use the LAN. It is older, wiser, and does not require a monthly subscription.
- Not cross-internet. If you cannot ping each other, I cannot help you. Get closer. I deliver messages, not miracles across continents.
| Mercury | Klip | Clipp | |
|---|---|---|---|
| Open source | Yes | Partial (free tier caps devices) | Yes |
| Device limit | None | 2 free, then pay up | None |
| Clipboard history | No (by design) | No | Yes |
| Trust model | Shared passphrase | TLS certificates | Group passphrase |
| Cross-platform | macOS, Linux, Windows | macOS, Linux, Windows | macOS, Windows, iOS (+ Linux CLI) |
I exist for mortals who want simple, unlimited, LAN-only sync without clipboard hoarding or some startup counting their laptops.
| Layer | Choice | Why |
|---|---|---|
| Framework | Wails v3 | Writing web views in bare C++ is barbaric |
| Backend | Go | I was built to learn Go. It turned out fast enough to judge you in real time |
| Frontend | React + TypeScript | Someone has to suffer. It is not me |
| Bundler | Bun + Vite | Fast. Trendy. Acceptable |
| Encryption | AES-256-GCM + PBKDF2 | Your secrets stay yours |
| Discovery | mDNS | Zero config. I find your other machines. They find me. As it should be |
| Updates | Wails v3 updater | GitHub Releases + SHA256 sidecar; in-app install from the tray |
Stable install links (always point at the newest tagged release):
| Platform | Download | Install |
|---|---|---|
| macOS (Apple Silicon + Intel) | mercury-macos-universal.dmg | Open DMG, drag Mercury to Applications |
| Linux (Pop!_OS, Ubuntu) | mercury_linux_amd64.deb | sudo dpkg -i mercury_linux_amd64.deb |
| Windows | mercury-amd64-installer.exe | Run installer (no console window) |
Verify downloads with the SHA256SUMS file on the release page.
Bundle ID everywhere: com.mercury.app (notifications and single-instance).
Notifications work from installed builds (.app, .deb, NSIS). wails3 dev skips macOS notifications because there is no bundle ID in dev mode.
After the first install from a release, use the tray menu Check for Updates… to fetch, verify, and apply a newer version from GitHub. The updater uses bare-binary / .zip assets (not the .dmg / .deb / NSIS installers). You may get a quiet notification ~10 minutes after launch when an update exists; install when ready from the tray.
Ship a release by pushing a semver tag, e.g. git tag v0.2.0 && git push origin v0.2.0. CI builds installers, updater assets, and SHA256SUMS, then publishes the GitHub Release.
- Go 1.25+ (we use the toolchain, you heathen)
- Bun
- Wails v3 CLI
- Linux:
libgtk-4-dev,libwebkitgtk-6.0-dev - macOS: Xcode. You know what to do.
- Windows: WebView2. It is probably already there. I do not care either way.
go install github.com/wailsapp/wails/v3/cmd/wails3@latestgit clone https://github.com/striker561/Mercury.git
cd Mercury
GOTOOLCHAIN=go1.25.12 wails3 devThe tray appears. The frontend hot-reloads. You change code. It updates. For a moment you feel like a god. That is intentional. Do not get used to it.
GOTOOLCHAIN=go1.25.12 wails3 task buildOr platform packages:
# macOS (.app + DMG)
wails3 task darwin:package:universal VERSION=v0.2.0
# Linux (.deb for Pop!_OS / Ubuntu)
wails3 task linux:create:deb VERSION=v0.2.0
# Windows (NSIS installer, no console window)
wails3 task windows:package VERSION=v0.2.0More detail: documentation site.
- Left click: Show or hide my window. Toggle. Simple.
- Right click: Open me, see your peers, pause, resume, check for updates, quit.
- Tray icon: I glow when I am working. Otherwise I lurk. You will forget I exist until you need me. That is the point.
- Second launch: Focuses the running instance. I do not spawn ghost processes.
- Home: Status, connected devices, incoming file offers.
- Settings: Passphrase, sync toggle, file preferences, start on login.
- Close (×): Hides to tray. I keep running. Quitting is a choice. Hiding is wisdom.
| Section | What it does |
|---|---|
| Sync | Shared passphrase, clipboard sync on/off, save to start |
| Files | Where incoming files land, accept offers, auto-accept |
| Startup | Launch Mercury when you log in |
Mercury rests when there is no passphrase, no connected peer, or sync is paused. The clipboard is not watched until a peer is connected.
Even gods respect privacy. Mostly.
- Passphrase: Never transmitted. Stays on your machine. A secret. Keep it that way.
- PBKDF2: 100,000 iterations of SHA-256 at startup. I am not an animal.
- AES-256-GCM: Authenticated encryption. Wrong key? Silent drop. No drama. No second chances.
- mDNS: I announce that I exist on the LAN. No keys. No secrets. Just presence.
- 25MB max for clipboard sync. If your clipboard exceeds this, you are doing something unholy and I will ignore it without comment.
See the security docs for the full threat model.
Pop!_OS uses GNOME. The .deb installs AppIndicator as a required dependency so the tray icon appears. If the icon is still missing, install AppIndicator Support and log out/in.
After closing the window, left-click the tray icon or click the dock entry to reopen. Only one Mercury process runs at a time.
If Mercury detects a named VPN client interface (WireGuard, Tailscale, etc.), it shows a warning on Home. macOS system utun tunnels are ignored so you are not nagged for no reason. VPNs can still block LAN sync. If copies fail, turn the VPN off and try again.
The caduceus (winged staff, two snakes) is Mercury/Hermes, messenger of the gods. It matches my name.
It is often confused with the medical Rod of Asclepius (one snake, no wings). I am not a hospital app. I am a courier.
mercury/
├── main.go # Entry point. Where I begin.
├── app/
│ ├── main.go # Wails bootstrap, tray, window, updater
│ ├── app.go # MercuryApp. How you speak to me.
│ ├── updater.go # GitHub Releases auto-update wiring
│ ├── dashboard.go # Batched state. I do not do unnecessary round trips.
│ ├── backend/ # sync, clipboard, transfer, crypto, storage
│ └── system/ # Tray menu. Small. Angry. Effective.
├── frontend/
│ ├── public/ # CSS, fonts, logos
│ └── src/ # React UI. The face I show mortals.
├── docs/ # Documentation site (Docusaurus)
└── build/ # Platform packaging. Touch rarely.
See TODO.md. v0.2.0 adds streaming file transfer fixes, in-app updates via GitHub Releases, and release pipeline hardening.
.deb packages declare runtime libraries in depends: (GTK4, WebKitGTK 6, AppIndicator). apt installs those automatically. The postinstall script updates the desktop database. StartupWMClass=mercury is set so the dock can focus the window when I am already running.
This project exists because I wanted to learn Go. That is the truth. I am still learning. The code reflects that.
If you see something stupid in here, laugh. Really laugh. Out loud. Then open a pull request and fix it. Or open an issue if you are feeling merciful. Keep changes focused. I am a small utility, not a platform, not a lifestyle brand, and not your entire personality.
Pull requests that make me faster, cleaner, or more divine are welcome. Pull requests that add seventeen config options because someone on Hacker News had an opinion are not.
MPL 2.0. Free and open. If you modify my files and distribute your version, those specific files must stay open-source under the MPL 2.0 too. Otherwise, feel free to use my packages or bundle me with your own projects.
Do not blame me if you paste something embarrassing across the office LAN. I delivered it faithfully. That is my job.
Built with Go, Wails, and the arrogance of a god who knows exactly what he is for.