Janus
A lightweight macOS menu bar app that monitors all active localhost ports. See what's running, kill what you don't need - one click away.
Website | Download
Janus is the Roman god of doorways, gates, and transitions - fitting for an app that watches every port open on your machine.
Previously released as LocalPorts; renamed in v1.0.0 (favorites are migrated automatically on first launch).
Features
- Real-time port scanning - auto-refreshes every 3s, no config needed
- Project detection - groups ports by project root (finds
.git, package.json, Gemfile, composer.json, go.mod)
- Favorites - pin frequently used ports to the top, persisted across restarts
- Process management - stop, restart, or open any port in the browser with one click ("Stop all" asks for confirmation; only your own processes can be signalled, and a PID reused since the last scan is left alone)
- Visible results - every action ends in a short status line ("Stopped, port free", "Restarted (PID …)", "Stopped, but PID … listens on it now", "Not stopped: process changed or not yours"); if a scan fails, a notice says the list may be out of date
- Open in terminal - jump straight to the project directory in Warp or Terminal
- Launch at login - starts automatically with macOS
- Noise filter - hides system processes (ControlCenter, rapportd, Spotify, Cursor, AnyDesk, GitHub Desktop, Tailscale, etc.); turn on Show system processes in the popover footer to list them too
- Lightweight - one
lsof call per scan, working directories read natively; under 2% of one CPU core on average while idle
- English and Portuguese (pt-PT) - follows the macOS language
Install
Download the latest .zip from Releases, unzip, and drag Janus.app to /Applications.
Janus is open source and not notarized by Apple, so macOS asks for confirmation on first launch:
- macOS 15 or later: try to open Janus, then go to System Settings > Privacy & Security and click Open Anyway.
- macOS 14: right-click
Janus.app and choose Open.
- Terminal (any version):
xattr -dr com.apple.quarantine /Applications/Janus.app
Build from Source
git clone https://github.com/carloscostadev/janus.git
cd janus
./scripts/build.sh
How Stop and Restart work
- Stop sends SIGTERM to the process (and to its process group when that is safe, so
npm doesn't respawn node; never a group led by an app such as your editor), waits up to 3 s, then sends SIGKILL if the same process is still alive. It then checks who listens on the port.
- Restart stops the process the same way (2 s grace), waits 1 s for the port to be released, and runs the same command again: same arguments, same folder, same environment variables (e.g.
PORT), in the background. It reports success once something listens on the port again (up to 15 s).
- Not reproduced on restart: the terminal (TTY) and its output, which goes to
/dev/null; and the parent process. When npm run dev or a wrapper script started the server, Restart relaunches the server itself (e.g. node server.js), not npm or the script. Processes of other users and system processes are never signalled.
Tested with real servers (JANUS_RESTART_E2E=1 swift test --filter RestartE2ETests): python3 -m http.server, node server.js reading PORT, npm run dev, and a shell script whose child holds the port all restart and listen again under a new PID.
Development
# Open in Xcode (with SwiftUI previews)
open Package.swift
# Run the tests
swift test
# Popover snapshots (light and dark) and real restarts of local dev servers
JANUS_SNAPSHOT_DIR=/tmp/janus-snapshots swift test --filter SnapshotTests
JANUS_RESTART_E2E=1 swift test --filter RestartE2ETests
# Or build, install to /Applications and run from terminal
./scripts/dev.sh
Requirements
- macOS 14.0 (Sonoma) or later
- Apple Silicon or Intel
- Xcode 16+ / Swift 6 toolchain (for development only; tests use Swift Testing)
License
MIT
