Fix what your Mac is doing
Short, practical answers with the Terminal commands that do it, and where Stat Space can show you the same thing live.
Ports & dev servers
“Address already in use” on Mac: find it, free it, or move
What EADDRINUSE and Errno 48 mean on macOS, how to find the process holding the port, and fixes for Node, Vite, Rails, Python, Docker and AirPlay on 5000/7000.
How to find orphaned Node processes on your Mac
Find node, vite, tsc and python processes still running after their terminal closed. They’re re-parented to launchd (PID 1). ps and pgrep commands to list and stop them.
How to find what’s using a port on your Mac
Find which process is listening on a port on macOS with lsof, see its project folder and parent, and decide whether to stop it.
How to kill the process using a port on your Mac
Stop whatever is listening on a port on macOS with lsof and kill, without killing your browser by mistake. Covers stubborn processes, Docker and launchd.
Is your dev server open to everyone on the Wi-Fi?
Check if your dev server is reachable from other devices, bind Next.js, Vite, Rails, Django, Flask, Express and Docker to localhost, and use the macOS firewall.
AI coding agents
How to check your Claude Code usage limits
See how much of your Claude Code 5-hour session and weekly limits you’ve used with /usage, claude.ai settings or a status line, and when each window resets.
How to check your Codex usage limits
Check how much of your OpenAI Codex 5-hour and weekly limits is left with /status, /usage and the status line, or read it from Codex’s local session logs.
How to clean up after a Claude Code session
Find and stop the dev servers, watchers, Docker containers and ports a Claude Code session left running on your Mac, and make cleanup automatic with a hook.
How to know when Claude Code is waiting for you
Stop checking the terminal. Make Claude Code ring a bell or post a macOS notification when it’s waiting for permission or input, with settings and hooks.
Let your coding agent see what’s running on your Mac
Give Claude Code, Cursor or Codex an MCP server that reports your Mac’s listening ports, CPU and memory load, top apps and leftover processes. Setup for each agent.
Sleep & power
How to keep your Mac awake
Stop your Mac sleeping during a build, download or agent run with caffeinate (-d, -i, -s, -t, -w), System Settings, or a menu bar app. Exact commands included.
How to keep your MacBook awake with the lid closed
How to keep an M-series MacBook running with the lid closed: clamshell mode with power and a display, or sudo pmset -a disablesleep 1, plus the heat and battery risks.
Why won’t my Mac sleep?
Find which app is keeping your Mac or its display awake with pmset -g assertions, fix the usual culprits (audio, browsers, Docker, caffeinate) and check wake reasons.
Performance & memory
High swap usage on a Mac: check it, understand it, reduce it
Check swap on macOS with sysctl vm.swapusage, see why it grows, whether it wears out your SSD, and how to bring it down without guesswork.
How much RAM do you need on a Mac for development?
Pick the right unified memory for coding, Docker and local LLMs on Apple Silicon, and use memory pressure on your current Mac to see if you need more.
How to find and fix high CPU usage on a Mac
Find what's using high CPU on your Mac with Activity Monitor, top and ps, tell normal spikes from runaway processes, and stop them safely.
Memory pressure on a Mac, explained
What the Memory Pressure graph in Activity Monitor means, what App Memory, Wired, Compressed and Cached Files are, and when you're actually short on RAM.
Which app is draining your Mac's battery?
See which apps drain your MacBook battery with Activity Monitor's Energy tab, the battery menu, top and powermetrics, and what to do about each one.
Why is my Mac slow? A five-minute diagnosis
A slow Mac is almost always CPU, memory pressure, heat or a full disk. Check each one in Activity Monitor and Terminal, then fix the one that's actually wrong.
Heat & fans
Controlling fan speed on an Apple Silicon Mac
macOS has no fan setting. Here's what manual fan control can and can't do on M-series Macs, how helper-based apps work, and when a fan curve is worth it.
How to check your Mac's temperature
macOS has no built-in temperature readout. Check thermal pressure with powermetrics, read real sensor values with a free tool, and know which number matters.
How to tell if your Mac is thermal throttling
Check whether macOS is slowing your Mac from heat with powermetrics and pmset -g therm, recognize the signs, and keep long builds running at full speed.
What's a normal temperature for an Apple Silicon Mac?
Typical CPU temperatures for M1 to M4 Macs at idle and under load, when throttling starts, how fanless MacBook Airs differ, and which readings to ignore.
Why is my Mac running hot, and what can I do about it?
Why your Apple Silicon Mac gets hot, when it's normal, how to find the app causing it, and practical ways to cool a MacBook down without hacks.
Storage
Can't eject a disk on your Mac? Find what's using it
Find which app is using a disk that won't eject on macOS with lsof, deal with Spotlight and Time Machine, and when force unmount is safe or not.
How to check your Mac's SSD health
Check your Mac's internal SSD wear with smartctl: percentage used, terabytes written, spare capacity and errors. What the numbers mean and when to worry.
How to free up disk space on a developer Mac
Reclaim tens of GB on a dev Mac: old node_modules, Xcode DerivedData and simulators, Docker images and Docker.raw, Homebrew and npm caches. Exact commands, safely.
Battery & devices
How to check your AirPods battery on a Mac
See your AirPods battery on a Mac from the menu bar, System Settings, the Batteries widget or Terminal, including left, right and case levels.
How to check your MacBook’s battery health
Check your MacBook battery health in System Settings, then get the real cycle count and capacity in mAh from system_profiler and ioreg.
How to check your USB-C charger’s wattage on a Mac
See what wattage your Mac negotiated with a USB-C charger, the voltages it offers, live input power, and the speed of every USB device.
Network
How to check your network latency on a Mac
Measure latency, jitter and packet loss on a Mac with ping and networkQuality, tell Wi-Fi problems from ISP problems, and keep a record over time.
How to see which app is using your network on a Mac
Find which app is using your internet on macOS with Activity Monitor and nettop, see live upload and download per process, and what to do about it.
How to track data usage on your Mac
macOS has no data usage meter. Here’s how to see bytes used per interface with netstat, per app with nettop, and save data on a hotspot.
Audio
How to see which app is using your microphone on a Mac
See which app is using your Mac’s microphone from the orange indicator and Control Center, check permissions, and revoke access for good.
How to set a different volume for each app on a Mac
macOS has no per-app volume mixer. Here are the built-in workarounds and the apps that add one, including how they work and what they ask for.
Know what your Mac is doing, without adding to it.
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