Localhost-Manager

Monitor active localhost ports · Host HTML files on real servers · Scan your local network · Completely local and private

👉 Visit our interactive Landing Page & Documentation Website

@Robotics-now

Install · Setup · Features · API Contract · File Structure

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⚡ Why Localhost Manager?

Tired of port conflicts (EADDRINUSE), guessing which dev server is on port 3000 vs 8080, or setting up full dev environments just to preview a static HTML snippet?

Localhost Manager gives you a clean control center directly in your browser toolbar to track, host, and inspect local services.

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✨ Features

Feature	Description
🔍 Port scanner	Monitors a configurable list of localhost ports and shows their status in real time
⚡ Auto scan	Probes all 65,535 ports in parallel batches — results cached for up to 24 hrs
📄 HTML hosting	Serves any HTML file on a real http://localhost port via the Node.js control server
🌐 Network scan	Optionally scans devices on your local network (192.168.x.x)
🎨 Themes	Light, dark, or auto (follows system appearance)
⬡ Live status dots	Green = active · Gray = offline · Blue = hosted · Red = error
↔️ Swipe to remove	Drag any port row left to reveal a delete button
Smart caching	Configurable scan interval (30 min → 24 hr) — popup opens instantly from cache
Acsent color picker	Adds much more personalization to Your extension
Clean UI	Check out the examples bellow!

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Install

Step 1 — Download the extension

Go to Releases and download the latest .zip. Extract it to a permanent folder — Chrome loads the extension directly from this folder so don't delete it after loading.

Step 2 — Load into Chrome

1. Open chrome://extensions
2. Enable Developer Mode (top right toggle)
3. Click Load unpacked
4. Select the port_ext extension folder inside the extracted files

The extension icon will appear in your toolbar.

Step 3 — Start the control server

The control server is required for the Host HTML feature. It runs a tiny local REST API that the extension uses to spin up and tear down real HTTP servers.

node server.js

Leave this terminal open while using the extension. You should see:

┌─────────────────────────────────────────┐
│  Localhost Manager Pro — Control Server │
│   Listening on http://127.0.0.1:8765    │
│   Keep this terminal open while using   │
│   the extension. Ctrl+C to quit.        │
└─────────────────────────────────────────┘

Requires Node.js or Python — no npm install needed, uses only built-in modules.

Important

When installing remember to load the port_ext file into your browser instead of the entire source code as it will fail because it is not the extension itself.

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Setup

Once installed, click the extension icon. Active services appear immediately with a green dot. Click any row to open it in a new tab.

Optional: Enable Auto Scan

Open Settings (gear icon in the popup) and toggle Auto scan on. The extension will probe every port from 1–65,535, cache the results, and only re-scan after your chosen interval.

30 min ──┬── 1 hr ── 2 hr ── ... ── 24 hr
         └── default: 2 hr

Inactive ports are automatically removed from the list when auto scan is on.

Host an HTML file

1. Make sure node server.js is running
2. Click Host HTML in the popup
3. Pick any .html file
4. The extension finds a free port in the 9000–9005 range, starts a real HTTP server, and opens it in a new tab
5. Click the stop button (swipe left on the row) to shut it down

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File Structure

Localhost-Manager/
├── manifest.json         # Extension manifest (MV3)
├── background.js         # Service worker
├── servers/
│   ├── server.js         # Node.js control server (run separately)
│   └── server.py         # Python version of the Node.js server 
├── templates/
│   ├── popup.html        # Extension popup UI
│   └── settings.html     # Settings page
└── scripts/
    ├── popup.js          # Popup logic
    └── settings.js       # Settings logic

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API Contract

The extension communicates with server.js over plain HTTP on http://127.0.0.1:8765. You can replace server.js with your own implementation in any language — as long as it speaks this contract.

Base URL: http://127.0.0.1:8765
All responses: Content-Type: application/json
CORS headers required on every response:

Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: GET, POST, OPTIONS
Access-Control-Allow-Headers: Content-Type

GET /status — health check

{
  "ok": true,
  "activePorts": [9000, 9001]
}

POST /start — serve an HTML file

Request body:

{
  "port": 9000,
  "content": "<html>...</html>"
}

Success:

{
  "ok": true,
  "port": 9000,
  "message": "Serving on http://localhost:9000"
}

Failure:

{
  "ok": false,
  "error": "Could not bind port 9000: address already in use"
}

POST /stop — shut down a hosted server

Request body:

{ "port": 9000 }

Success:

{
  "ok": true,
  "port": 9000,
  "message": "Stopped server on port 9000"
}

Failure:

{
  "ok": false,
  "error": "No server running on port 9000"
}

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Settings Reference

Setting	Description
Theme	Light / Dark / Auto (follows system)
Grid view	Toggle between list and icon grid layout
Auto scan	Discover all active ports automatically
Scan interval	How long to cache auto scan results (30 min – 24 hr)
Local network scan	Scan 192.168.x.x devices on common ports

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Status Indicators

Dot	Meaning
🟢 Green	Port is active and responding
⚫ Gray	Port is in your list but not responding
🔵 Blue	Port is being hosted by the extension
🔴 Red (pulsing)	Error — e.g. control server offline
🟡 Yellow (pulsing)	Scanning in progress

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Browser Compatibility

Works on any Chromium-based browser with Manifest V3 support:

• Google Chrome
• Microsoft Edge
• Opera
• Chromium

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Quick Reference

Control server port	8765
Hosted file ports	9000 – 9005
Auto scan range	1 – 65,535
Cache interval	30 min – 24 hr
Network scan range	192.168.x.1 – .30 (configurable)
Manifest version	MV3
Node.js required	For Host HTML feature only
Security	100% private. Runs entirely locally on your machine.

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Releases version numbers

The first number is the extension's version, the second number is the major update and finaly the third one are the minor updates.

Built for developers who run too many servers.

---- Releases ----

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License

GPL 3.0 License
Copyright © 2026 Robotics-now