localhost:9090: Prometheus and Cockpit
Port 9090 is Prometheus’s default and also used by Cockpit. How to open it and fix DOWN targets and conflicts.
Open this address: http://localhost:9090This opens on your own computer. It only works if the program is running.
localhost:9090 opens the Prometheus web page. On many Linux servers the Cockpit console uses the same port, which causes confusion.
What runs on localhost:9090
- Prometheus web page and API (default port 9090)
- Cockpit, the Linux web console, also uses 9090
- Targets, graphs and alerts live here
Commands to start and test port 9090
prometheus --config.file=prometheus.ymlcurl http://localhost:9090/-/healthydocker run -p 9090:9090 -v ./prometheus.yml:/etc/prometheus/prometheus.yml prom/prometheuscurl -X POST http://localhost:9090/-/reloadFind what is using port 9090
Run these in a terminal on your computer. Nothing is sent to this site.
If localhost:9090 will not open
- You see a Linux login page, not Prometheus
- Cockpit uses port 9090 too. Start Prometheus on another port with --web.listen-address=:9091.
- Targets show as DOWN
- Prometheus cannot reach the target. Check the address, port and firewall in prometheus.yml.
- Config reload returns 403
- Start Prometheus with --web.enable-lifecycle to allow reloads.
- Port 9090 is in use
- Find the program with the tool below.
Other ports like 9090
| Port | Usually used by |
|---|---|
| localhost:11434 | Ollama (AI models) |
| localhost:5601 | Kibana |
| localhost:11501 | Not a standard port: check what is using it |
| localhost:9200 | Elasticsearch |
| localhost:5672 | RabbitMQ |
| localhost:15672 | RabbitMQ admin page |
| localhost:9229 | Node.js debugger |
Questions about localhost:9090
- What is port 9090?
- Prometheus by default, and also the Cockpit web console on Linux.
- How do I see my targets?
- Open localhost:9090/targets in the browser.
- Is localhost:9090 safe?
- Yes while it stays on localhost. Tools like this often show sensitive data, so keep them off the public internet and put a login in front of them if other people can reach the port.
- Can I use a different port instead of 9090?
- Yes. Pick a free port above 1024, set it in the program, and open that number instead. If other programs connect to this port, change it there as well.
- How do I check what is using port 9090?
- Use the port checker on this page. It shows the command for Windows, macOS and Linux and does not send anything to this site.
Free tools that help
- Common ports listSearch a list of common TCP and UDP port numbers: SSH 22, HTTP 80, HTTPS 443, MySQL 3306, PostgreSQL 5432 and more, with dev server ports.