What's running on my Mac? How to see every dev server and port

When working on a Mac, it can be easy to lose track of what applications and dev servers are running in the background. To get a clear picture of all active processes, use the command "lsof -nP -iTCP -sTCP :LISTEN" in Terminal. This lists every TCP port that something is listening on, along with the program and its Process ID (PID).

For example, a typical afternoon might reveal processes like "node 48213" listening on port 3000, "php 52210" on port 8000, "postgres 611" on port 5432, and "redis-ser 702" on port 6379. Port 3000 enables connections from other devices on your network, while 127.0.0.1 or [::1] implies that only this Mac can access it.

Some processes may appear twice, once for IPv4 and once for IPv6, sharing the same PID. To find out which project a server belongs to, use "ps -p PID -o command=" along with "lsof" to identify the project name (e.g., node or php).

Ports not bound to 127.0.0.1 or [::1] can be reached from your network, making them useful for testing on phones or café Wi-Fi. To check for reachable processes, run "lsof -nP -iTCP -sTCP :LISTEN | grep -vE 127.0.0.1|\[::1\]".

Most development servers only listen on localhost unless you explicitly specify a different host (Vite) or -H 0.0.0.0 (Next.js). Ports used by Docker and Homebrew services appear as the database or service name in "lsof" output, not as the specific app name.

While Activity Monitor provides information on CPU and memory usage, it doesn't show which ports are being used. To get a more comprehensive view of your Mac's processes, consider using a third-party tool like Portlivo, a Mac menu bar app that keeps a live list of servers, their commands, uptime, answering status, CPU and memory usage, and Docker/Homebrew services.