Xcode
Apple's official IDE. Mac-exclusive. The only officially supported way to build apps for iOS/iPadOS/macOS/watchOS/tvOS/visionOS. Free download via the Mac App Store.
Includes: editor (LSP support since v15), Interface Builder (Storyboards), SwiftUI Preview, Simulator (iOS/visionOS emulation), Instruments (profiler), Source Editor with refactoring + AI (Predictive Code Completion since 16). Size: ~50 GB installed. Notoriously memory-hungry + frequently updated. Competitors (unofficial): AppCode (JetBrains, deprecated 2022), VS Code with Swift extension (rapidly growing for cross-platform Swift), Cursor.