How to Check Which Process Is Using a Specific Port on Your System

Key takeaways

• Use ss -ltnp 'sport = :8080' on Linux, lsof -i :8080 on macOS, and netstat -aon with tasklist on Windows.
• Confirm what the PID actually is before killing it, since stopping the wrong process can take down a production service.
• Prefer reconfiguring the service to another port over killing a process, and run the lookup with sudo or you may see nothing.

A port conflict stops a service from starting, usually with an "address already in use" error. The fix is always the same two steps: find the PID bound to the port, then decide whether to reconfigure or stop that process. Here are the current commands for each operating system.

How do I check which process is using a port on Linux?

Use ss, the modern replacement for netstat. It is installed by default on current distributions.

sudo ss -ltnp 'sport = :8080'

The flags mean listening (-l), TCP (-t), numeric ports (-n) and show the process (-p). A typical line ends with users:(("nginx", pid=2345, fd=6)), so the PID is 2345. For UDP, swap -t for -u.

lsof gives the same answer with the owning user and command name:

sudo lsof -i :8080

If a system still has the legacy net-tools package, netstat works too:

sudo netstat -tulpn | grep :8080

Run these with sudo. Without it, Linux hides the PID and program name for sockets you do not own, which is the most common reason the process column comes back empty.

How do I check which process is using a port on Windows?

Open Command Prompt or PowerShell as Administrator. In Command Prompt, list the port and its PID:

netstat -aon | findstr :8080

The last column is the PID, for example 1234. Turn that into a program name:

tasklist | findstr 1234

PowerShell does both steps at once and is cleaner:

Get-Process -Id (Get-NetTCPConnection -LocalPort 8080).OwningProcess

How do I check which process is using a port on macOS?

lsof is the simplest tool on macOS and behaves the same as on Linux:

sudo lsof -i :3000

The output lists the command, PID and user bound to the port. netstat exists on macOS but no longer maps ports to PIDs cleanly, so prefer lsof here.

Confirm what the process is before you touch it

A PID on its own is not enough. Check the full command line so you do not stop something important:

• Linux or macOS: ps -p 2345 -o pid, user, comm, args
• Windows (PowerShell): Get-Process -Id 1234 | Format-List Name, Path, Description

If the program is a database, a system service or something you do not recognise, investigate rather than kill it. A process listening on an unexpected port is worth checking against what you expect to be running.

How do I free a port that is already in use?

You have two choices once you know the owner. The cleaner option is to change the port in the application's own configuration, which avoids repeating the conflict. If you do need to stop the process, do it by PID.

Try the graceful stop first. kill -9 and /F give the program no chance to flush data or close files, so keep them for processes that will not exit any other way, and never use them on a critical service without understanding the consequences.

Common mistakes and quick fixes

• Empty process column: you forgot sudo (Linux/macOS) or Administrator rights (Windows).
• Nothing found, but the app still fails: the port may be held on another interface or by IPv6. Drop the filter and scan everything with sudo ss -ltnp or netstat -aon, then read the full list.
• Port freed but reappears instantly: a service manager such as systemd or a Docker restart policy is relaunching the process. Stop the service or container, not the child PID.
• Docker binding failures: check the host side with sudo ss -ltnp; a previous container or the Docker proxy often still holds the published port.

Quick command reference

These few commands cover almost every port conflict you will meet as a developer or administrator. If you want to go deeper into the Linux side, see our guide to process management in Linux and the essential Linux networking commands every administrator should know. Structured practice with these tools is part of a Linux training course if you want a guided path.

Related reading

• A Practical Guide to Windows Firewall | Configuring Inbound and Outbound Rules with Real-Time Testing
• How to Diagnose Firewall and Port Blocking Issues: A Step-by-Step Guide (2026)
• Most Commonly Used TCP and UDP Ports List with Services for Ethical Hacking, Networking, and Cybersecurity (Updated 2026 Guide)