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portcheck vs lsof

Both tools answer a local debugging question, but they sit at different levels of abstraction. portcheck gives you the fast port-specific read: PID, command, user, and bind address. lsof is the broader file-descriptor hammer. Pick the one that matches how wide you need to sweep.

lsof alternative what's on :3000? local port listener kill stuck port

Use portcheck when

  • You want the quickest answer to "what is listening on this port?"
  • You need to audit a local service, find a mystery listener, or confirm a deploy actually bound
  • You want a scan-friendly table with PID, command, user, and bind address
  • You are in CI, a VPN, or an airgapped environment and need zero external dependencies
  • You want a port-focused helper that is easy to read at a glance

Use lsof when

  • You need the canonical Unix sweep for files, sockets, pipes, locks, and descriptors
  • You already have muscle memory around `lsof` and want the broadest possible view
  • The port question is just one piece of a larger process or file investigation
  • You do not mind denser output if it gives you the whole machine in one command
  • You are comfortable trading readability for breadth

Feature comparison

Feature portcheck lsof
Primary use caseLocal port listener auditFile-descriptor and socket inspection
Shows process/PID/user✓ yes — PID, command, user, address✓ yes — broad ownership context
Works offline / no internet✓ fully offline✓ fully local
Readability at a glance✓ scan-friendly, port-first— denser, broader output
Scriptable / automatable✓ JSON output, pipe-friendly✓ scriptable, but noisier
Kill stuck port workflows✓ built around the port question✓ possible, but less focused
Best for CI / containers✓ zero external deps✓ if the process table is visible
No telemetry / data sent✓ nothing leaves the machine✓ nothing leaves the machine
Open source✓ MIT license✓ bundled with the OS / distro
Free✓✓

Frequently asked questions

Is voiddo portcheck an alternative to lsof?
Sometimes, yes. They overlap around the local "what is using this port?" question, but they are not the same tool. portcheck is tuned for the quick port-specific read. lsof is the broader file-descriptor hammer.
Does voiddo portcheck require internet access?
No. portcheck runs entirely on your local machine with zero external dependencies. It reads local kernel socket tables and process data, so it works in airgapped environments, CI containers, and VPNs where outbound traffic is restricted.
Can portcheck replace lsof entirely?
No. lsof still wins when you need the broadest view of files, sockets, pipes, locks, and descriptors. portcheck wins when you want the narrow question answered fast and in a scan-friendly layout.
What information does portcheck show that lsof does not?
portcheck focuses the answer on the port question: PID, command/binary name, user, and bind address, plus JSON output for scripts. That narrower view is why it reads so quickly when you are in the middle of a debugging session.
Is voiddo portcheck free?
Yes. portcheck is free, MIT-licensed, and open source. No account, no ads, no telemetry, no rate limits. It is part of the free developer tools at tools.voiddo.com.

Need the local port answer now?

Compare portcheck to lsof, then open the tool that gives you the fastest honest answer for the debugging job in front of you.

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