Xcode

Backup Xcode defaults

defaults read com.apple.dt.Xcode > ~/Desktop/XcodeDefaults.plist

Restore Xcode vanilla defaults

If you delete/move the current plist, Xcode will write a fresh one next time you run it.

killall Xcode
mv ~/Library/Preferences/com.apple.dt.Xcode.plist ~/Desktop/XcodeDefaults.plist
open -b com.apple.dt.Xcode

Enable project build time

defaults write com.apple.dt.Xcode ShowBuildOperationDuration -bool YES

Enable parallel builds for Swift

defaults write com.apple.dt.Xcode BuildSystemScheduleInherentlyParallelCommandsExclusively -bool YES

Disable parallel builds for Swift

Xcode 9.3 now runs more Swift build tasks in parallel with other commands. This may improve build times for Swift projects, but may also increase memory use during the build. This feature can be disabled from Terminal by setting a user default with

defaults write com.apple.dt.Xcode BuildSystemScheduleInherentlyParallelCommandsSerially -bool YES

Enable multi-cursor editing

defaults write com.apple.dt.Xcode PegasusMultipleCursorsEnabled -bool YES

Enable maximum number of concurrent compile tasks

defaults write com.apple.dt.Xcode IDEBuildOperationMaxNumberOfConcurrentCompileTasks `sysctl -n hw.ncpu`

Enable extensive per operation timing logs

defaults write com.apple.dt.Xcode IDEBuildOperationTimingLogLevel -int 3

Enable/Disable indexing

Enable indexing

defaults delete com.apple.dt.Xcode IDEIndexDisable
defaults write com.apple.dt.XCode IDEIndexEnable -bool YES

Disable indexing

defaults delete com.apple.dt.Xcode IDEIndexEnable
defaults write com.apple.dt.XCode IDEIndexDisable -bool YES

Show Indexing numeric progress

defaults write com.apple.dt.Xcode IDEIndexerActivityShowNumericProgress -bool YES

Show prebuild step logs

defaults write com.apple.dt.Xcode IDEShowPrebuildLogs -bool YES

Set SourceKit log level

If set to SourceKit will write a log to /tmp with all the details of what it is doing while indexing. A lot of people find they have header hygiene problems or module problems that happen to work while building in certain configurations but aren't actually correct, resulting in missing modules or broken headers from the indexer's point of view. May not work anymore.

defaults write com.apple.dt.Xcode IDESourceKitServiceLogLevel -int 3 

Enable internal Xcode (debug) menu

defaults write com.apple.dt.Xcode ShowDVTDebugMenu -bool YES

Disable automatic reopening of last project

Prevents Xcode from automatically restoring the last open project. This enables running multiple Xcode versions for different projects.

defaults write com.apple.dt.Xcode ApplePersistenceIgnoreState -bool YES

Some minimal additional logging

defaults write com.apple.dt.XCBuild EnableDebugActivityLogs -bool YES

Enable build debugging mode

This slows down the build system & litters DerivedData//Build/Intermediates.noindex), generally should only be enabled when trying to capture a trace for incremental build debugging purposes.

defaults write com.apple.dt.XCBuild EnableBuildDebugging -bool YES

Simulator

Enable Simulator fullscreen mode

defaults write com.apple.iphonesimulator AllowFullscreenMode -bool YES

XCBuild

Enable Build Debugging

Creates an XCBuildData folder in ~/Library/Developer/Xcode/DerivedData/<your target>/Build/Intermediates.noindex/ which contains debugging info for xcodebuild.

defaults write com.apple.dt.XCBuild YES