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Port 5353 · UDP

Port 5353: mDNS (local device discovery)

Multicast DNS: finding devices by name on the local network without a DNS server, over 224.0.0.251. Used for printers, Chromecasts and AirPlay devices.

Protocol
UDP
On Windows
svchost.exe (DNS Client) and browsers
Risk if open to the internet
Medium

Seeing it on your PC

svchost.exe, Chrome, Edge, Spotify or iTunes on 5353 are looking for devices. Normal.

Should you block it?

Local network only. It never needs to cross the internet.

Check it on your PC

Run this in PowerShell to see what is using port 5353 right now, and which program owns it:

Get-NetUDPEndpoint -LocalPort 5353 -ErrorAction SilentlyContinue | Select-Object LocalAddress,LocalPort,@{n='Process';e={(Get-Process -Id $_.OwningProcess -ErrorAction SilentlyContinue).ProcessName}}

No output means nothing is using the port at the moment. For every connection at once, paste netstat -ano into the netstat explainer.

Block it in Windows Firewall

In PowerShell run as administrator, this stops other computers from connecting to this port on your PC. It does not stop your own programs connecting out.

New-NetFirewallRule -DisplayName "Block inbound UDP 5353" -Direction Inbound -Protocol UDP -LocalPort 5353 -Action Block

Undo it with Remove-NetFirewallRule -DisplayName "Block inbound …", using the same name. If you depend on the service on your local network, this rule stops that too.