How to: Find Which Application Is Using a Specific Port on Windows

TL;DR — Quick Summary

Find which Windows application is using a specific port using netstat, PowerShell Get-NetTCPConnection, Resource Monitor, and TCPView. Resolve port conflicts and free up ports for your services.

Finding Which Application Uses a Specific Port on Windows

Port conflicts are one of the most common issues when running multiple services on Windows. When you get “port already in use” or a service fails to start, you need to identify which process is occupying the port.

Method 1: netstat (Command Prompt)

Open an elevated Command Prompt (Run as Administrator):

netstat -ano | findstr :80

Output example:

  TCP    0.0.0.0:80    0.0.0.0:0    LISTENING    4
  TCP    0.0.0.0:443   0.0.0.0:0    LISTENING    4

The last column is the PID (Process ID). Find the process name:

tasklist | findstr 4

Useful netstat Flags

Flag	Description
`-a`	Show all connections and listening ports
`-n`	Show addresses and port numbers numerically
`-o`	Show the owning process PID
`-b`	Show the executable name (requires admin)
`-p TCP`	Show only TCP connections

:: Show all listening ports with process names
netstat -anob | findstr LISTENING

:: Show only TCP connections on a specific port
netstat -ano -p TCP | findstr :8080

:: Show all established connections
netstat -ano | findstr ESTABLISHED

Method 2: PowerShell (Recommended)

PowerShell provides a cleaner one-liner:

# Find which process uses port 80
Get-Process -Id (Get-NetTCPConnection -LocalPort 80).OwningProcess

# Show details with port state
Get-NetTCPConnection -LocalPort 80 | Select-Object LocalPort, State, OwningProcess, @{Name="Process";Expression={(Get-Process -Id $_.OwningProcess).ProcessName}}

# Find all listening ports
Get-NetTCPConnection -State Listen | Select-Object LocalPort, OwningProcess, @{Name="Process";Expression={(Get-Process -Id $_.OwningProcess).ProcessName}} | Sort-Object LocalPort

# Check UDP ports
Get-NetUDPEndpoint -LocalPort 53 | Select-Object LocalPort, OwningProcess

Method 3: Resource Monitor (GUI)

Press Win+R, type resmon, press Enter.
Click the Network tab.
Expand Listening Ports.
Sort by Port to find the process using your port.

Method 4: TCPView (Sysinternals)

Download TCPView from Sysinternals. It provides a real-time GUI showing all TCP/UDP connections, their state, and the process using them. You can right-click to kill a process directly.

Commonly Conflicting Ports

Port	Common Services
80	IIS, Apache, Nginx, Skype (legacy)
443	IIS, Apache, Nginx (HTTPS)
3306	MySQL, MariaDB
5432	PostgreSQL
1433	SQL Server
8080	Tomcat, development servers, proxies
3000	Node.js (Express, React dev)
5000	Python (Flask), Docker Registry
3389	Remote Desktop (RDP)
53	DNS (Windows DNS Server, Pi-hole)

Freeing Up a Port

Stop the Process

:: Force kill by PID
taskkill /PID 1234 /F

:: Kill by process name
taskkill /IM httpd.exe /F

Stop a Windows Service

:: Stop IIS
net stop w3svc

:: Stop a specific service
net stop "Service Name"

Or use services.msc to stop the service graphically.

Check from Outside (Remote Port Test)

# PowerShell
Test-NetConnection -ComputerName 192.168.1.100 -Port 80

# CMD
telnet 192.168.1.100 80

Frequently Asked Questions

How do I find which application is using a specific port on Windows?

Method 1 (CMD): Run 'netstat -ano | findstr :PORT' to find the PID, then 'tasklist | findstr PID' to identify the process. Method 2 (PowerShell): Run 'Get-Process -Id (Get-NetTCPConnection -LocalPort PORT).OwningProcess'. Method 3: Open Resource Monitor > Network > Listening Ports.

How do I free up a port being used by another application?

First identify the process with netstat or PowerShell. Then stop it: via Task Manager (right-click > End Task), via services.msc for Windows services, or via command line: 'taskkill /PID process_id /F'. For services like IIS or SQL Server, stop them through their management console.

What does 'port already in use' or 'address already in use' mean?

It means another process is already listening on the port your application needs. Only one process can bind to a specific port at a time. Common conflicts: port 80 (IIS vs Apache vs Nginx), port 443 (HTTPS), port 3306 (MySQL), port 5432 (PostgreSQL), port 8080 (development servers).

How do I check if a port is open from outside?

From another machine, use: 'Test-NetConnection -ComputerName SERVER -Port PORT' (PowerShell), 'telnet SERVER PORT' (CMD), or 'nmap -p PORT SERVER' (Linux). If the port is open locally but blocked externally, check Windows Firewall rules.