API Testing for Purists.
Instant startup. 60fps UI. $0 forever.

Documentation • Download • Roadmap • Philosophy • Contributing

Mercury uses ~100MB RAM to render at 60fps with native GPU acceleration. Electron apps use 500MB+ to feel like a slow website.

"Build half a product, not a half-assed product." — 37signals

Mercury is built on principles, not features:

• ⚡ Native Rust — Real performance, not wrapped web pages
• 📁 Files, not databases — Your requests are just files. Grep them. Git them.
• 🔒 Truly local — We don't have servers. Your secrets stay yours.
• ⌨️ Keyboard-first — Your hands never leave the keyboard
• 🚫 No bloat — No AI, no collaboration, no features you'll never use

brew install --cask harry-kp/tap/mercury

Then launch from Applications or run mercury in terminal.

macOS / Linux:

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/Harry-kp/mercury/releases/latest/download/mercury-installer.sh | sh

Windows (PowerShell):

irm https://github.com/Harry-kp/mercury/releases/latest/download/mercury-installer.ps1 | iex

Then launch:

mercury

💡 If you get "command not found", restart your terminal or run source ~/.zshrc

The installer puts mercury in ~/.cargo/bin. If you prefer launching from Spotlight/Start Menu:

# One-liner: creates Mercury.app you can add to Dock
mkdir -p /Applications/Mercury.app/Contents/MacOS && \
cp ~/.cargo/bin/mercury /Applications/Mercury.app/Contents/MacOS/ && \
cat > /Applications/Mercury.app/Contents/Info.plist << 'EOF'
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>CFBundleExecutable</key>
    <string>mercury</string>
    <key>CFBundleName</key>
    <string>Mercury</string>
    <key>CFBundleIdentifier</key>
    <string>com.mercury.app</string>
</dict>
</plist>
EOF

cat > ~/.local/share/applications/mercury.desktop << 'EOF'
[Desktop Entry]
Name=Mercury
Exec=$HOME/.cargo/bin/mercury
Type=Application
Categories=Development;
EOF

# Extract and run
tar -xf mercury-*.tar.xz && chmod +x mercury && ./mercury

git clone https://github.com/Harry-kp/mercury.git
cd mercury
cargo build --release
./target/release/mercury

Your requests are stored as JSON files. Version control friendly. No lock-in.

{
  "method": "GET",
  "url": "https://api.example.com/users",
  "headers": {},
  "body": ""
}

{
  "method": "POST",
  "url": "https://api.example.com/users",
  "headers": {
    "Content-Type": "application/json",
    "Authorization": "Bearer {{token}}"
  },
  "body": "{\"name\": \"John Doe\", \"email\": \"john@example.com\"}"
}

Variables like {{token}} are loaded from .env files in your workspace.

• Live File Sync — Edit in VS Code, updates instantly. Two-way sync.
• Auto-Save — Changes are persisted immediately. Never lose work.
• Collections — Organize requests in folders
• Environments — .env file support with {{variable}} syntax
• History — Timeline of all requests with restore
• Focus Mode — Distraction-free editing
• cURL Import — Paste cURL commands directly
• Collection Import — Import from Postman or Insomnia
• Request Cancellation — Stop runaway requests instantly
• Syntax Highlighting — JSON responses beautifully formatted
• Dark Mode — Easy on the eyes, built for late nights
• Automatic Cookies — Auth flows work seamlessly

Mercury uses sensible defaults so you can focus on your API, not configuration:

We intentionally don't build:

• ❌ Cloud sync
• ❌ Team collaboration
• ❌ AI assistants
• ❌ Plugins/extensions
• ❌ User accounts
• ❌ Analytics/telemetry

These aren't missing features. They're features we chose not to build.

Mercury is open source. PRs welcome.

# Development
cargo run

# Tests
cargo test

# Release build
cargo build --release

MIT License — do whatever you want.

Built with obsessive minimalism.
@Harry-kp