Port 9090 (Prometheus)

Prometheus server web UI and HTTP API. Cockpit (Linux web console) also uses 9090.

Registered (user) port, 1024-49151 TCP Monitoring and logging Do not expose to the internet

What port 9090 is used for

Prometheus server web UI and HTTP API. Cockpit (Linux web console) also uses 9090.

Security: should port 9090 be open?

Do not expose to the internet. Prometheus has no built-in authentication by default; an exposed server leaks hostnames, internal IPs and metrics, and the admin API can delete data if enabled. Keep it internal or add a reverse proxy with auth.

IANA assignment

Service nameProtoDescriptionAssigneeReference

websm TCP WebSM I Hsing Tsao -

websm UDP WebSM I Hsing Tsao -

Check what is listening on port 9090

Linux: is anything listening on TCP 9090?

sudo ss -tlnp 'sport = :9090'

Linux / macOS: which process owns the port

sudo lsof -nP -i :9090

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':9090 '

Windows (Command Prompt)

netstat -ano | findstr :9090

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 9090 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine

nc -vz -w 5 HOST 9090

From Windows

Test-NetConnection HOST -Port 9090

Block port 9090 in the firewall

ufw

sudo ufw deny 9090/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 9090 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 9090 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 9090' -Direction Inbound -Protocol TCP -LocalPort 9090 -Action Block

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.