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Undo the last Git commit and keep your changes with git reset --soft HEAD~1. Tested reset modes, revert, amend, reflog recovery and pushed commits.

Run ssh-keygen -t ed25519 -C "you@example.com", save the passphrase in Keychain, copy the key with pbcopy and add it to GitHub. Tested on macOS 26.

Find large files on a Mac with find ~ -xdev -type f -size +1G, or instantly with mdfind. Tested timings, du sizing, and what is safe to delete.

Press Cmd+Shift+Period in Finder to show hidden files on Mac. Plus ls -a, the permanent defaults command, and chflags to hide or unhide any file.

Flush DNS on macOS Tahoe with: sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder. Then check it worked, and see when flushing won't help.

Find what is using a port with lsof -nP -iTCP:8080 -sTCP:LISTEN, then kill it by PID. Plus why ports 5000 and 7000 are taken by AirPlay on macOS.

Run ipconfig getifaddr en0 to get your Mac's local IP, and curl -4 -s https://ifconfig.me for your public IP. Tested on macOS Tahoe with real output.

Check MacBook battery health in System Settings > Battery, or run system_profiler SPPowerDataType for cycle count, condition and maximum capacity.

See what is using RAM on a Mac with top -l 1 -o mem, memory_pressure and vm_stat. Tested on Apple Silicon, with swap, compression and GB conversion.

Run caffeinate -d to keep your Mac's screen on until you press Ctrl+C, or caffeinate -d -t 3600 for one hour. Every flag tested on macOS Tahoe.

On Apple Silicon, Homebrew lives in /opt/homebrew/bin. Add eval "$(/opt/homebrew/bin/brew shellenv)" to ~/.zprofile. Fixes for python, pip, npm and code too.

Add export MY_VAR=value to ~/.zshrc (or ~/.zprofile for PATH), then run source ~/.zshrc. Tested on macOS Tahoe with zsh 5.9, plus the temporary way.