Browser Port Scanner
Perform network reconnaissance directly from your browser. Scan localhost development servers or check outbound connectivity to public IPs.
Modern browsers block outgoing requests to “unsafe” ports (e.g., FTP 21, SSH 22, SMTP 25). Furthermore, we cannot accurately scan *inbound* ports from the internet using Javascript. This tool uses fetch-timing heuristics to check local development ports (e.g., 3000, 8080) and standard HTTP/WebSocket outbound ports.
System initialized. Ready for scanning protocol.
Targeting strictly permitted browser ports.
How it works (The Fetch Hack)
Since browsers don’t have access to raw TCP/UDP sockets, this tool uses the Javascript fetch() API with mode: 'no-cors'.
If a port is completely closed, the connection is instantly refused, resulting in a fast error (usually < 20ms). If the port is open and listening, the connection connects, and the server either responds or hangs, taking significantly longer. We measure this time difference (Timing Attack Heuristics) to deduce if the port is Open or Closed.
Common Localhost Ports
- 3000: React / Next.js
- 4200: Angular CLI
- 5000: Flask / .NET Core
- 5173: Vite.js
- 8000: Django / Laravel
- 8080: Vue.js / Tomcat