Port 9090: Prometheus
Port 9090 is the default web interface and API port for Prometheus, the open-source metrics and monitoring system. Individual exporters that feed data into Prometheus typically run on their own ports, such as 9100 for the Node Exporter.
| Port number | 9090 |
|---|---|
| Service | Prometheus monitoring web UI |
| Protocol | TCP |
| Category | Web |
| Default encryption | No |
How do I check whether port 9090 is open?
Port 9090 carries TCP, so a connection either completes its handshake or it does not, which makes the check definitive.
| Question | Command | What to know |
|---|---|---|
| Is it open on a remote host? | nc -vz example.com 9090 | A TCP handshake either completes or it does not, so netcat gives a definitive answer in one line. |
| Same check on Windows | Test-NetConnection example.com -Port 9090 | Built into PowerShell. TcpTestSucceeded in the output is the answer; telnet is not installed by default on modern Windows. |
| What is listening locally? | ss -tlnp | grep ':9090 ' | Lists the process bound to port 9090 on Linux. On macOS use lsof -nP -iTCP:9090 -sTCP:LISTEN, on Windows netstat -ano | findstr :9090 |
Replace example.com with the host you are testing. A blocked port and a port with nothing listening on it look identical from the outside, so if a service should be running, check locally before blaming the firewall.
Frequently asked questions
What is port 9090 used for?
Port 9090 is the default web interface and API port for Prometheus, the open-source metrics and monitoring system. Individual exporters that feed data into Prometheus typically run on their own ports, such as 9100 for the Node Exporter.
Is port 9090 TCP or UDP?
Port 9090 (Prometheus) uses TCP.
Is port 9090 secure?
Port 9090 is not encrypted by default. Where possible, use an encrypted alternative or tunnel it over TLS or a VPN.
Should I open port 9090 on my firewall?
Only if you specifically need Prometheus. Expose it to the smallest set of trusted sources, and never open database or Windows-service ports to the whole internet.