For most people the best Mac keyboard remapping app is Karabiner-Elements, because it's open source and handles everything from a single key swap to complex rules. Before you install anything, though, check System Settings: macOS can already turn caps lock into Control, or switch it off, on its own.
Start with what your Mac already does
Plenty of people go hunting for an app when the fix is two menus deep. Apple's own route, from its Mac User Guide: choose Apple menu, System Settings, click Keyboard in the sidebar, click Keyboard Shortcuts, then Modifier Keys. Each modifier gets a pop-up menu where you pick a different action or No Action, so caps lock can become Control in about ten seconds. Restore Defaults puts everything back if you change your mind.
In the same window, App Shortcuts lets you give any menu command a new shortcut, for one app or for all of them. Click the plus button, pick the app, type the menu item's name exactly as it appears in the menu, then press the keys you want. It's the fastest way to fix a shortcut you hate in one program without touching the rest of the system.
There's one more built-in route for the comfortable-with-Terminal crowd, and it isn't limited to modifiers: Apple's own example swaps the A and B keys. Apple's technical note TN2450 documents the hidutil command for remapping keys, using the key codes in its own table (caps lock is 0x39, Escape is 0x29). This line turns caps lock into Escape: hidutil property --set '{"UserKeyMapping":[{"HIDKeyboardModifierMappingSrc":0x700000039,"HIDKeyboardModifierMappingDst":0x700000029}]}'. Apple's note says remappings are lost when the system restarts, so treat it as an experiment rather than a permanent setup.
If none of that covers what you need, you're into third-party territory, and what you want the key to do decides which kind of app.
Remap, macro or script: three different jobs
The tools on this page do three jobs that look alike from a distance. A remapper changes what a key is: caps lock becomes Control, the right Option key becomes Delete, a gaming mouse button becomes Command. A macro or shortcut app changes what a key does: press a combination and it opens an app, types a block of text or runs a ten-step workflow. A scripting bridge lets you write code that reacts to keyboard and mouse events, which is unlimited and also a hobby in itself.
Apps that change what a key is
Karabiner-Elements
An open-source keyboard customiser living in the menu bar, covering simple one-to-one swaps and far more complex modifications.
Hyperkey
Want caps lock to become a hyper key that presses all four modifiers at once? This small menu bar app does exactly that.
USB Overdrive
Owners of third-party USB or Bluetooth mice, keyboards, trackballs and gamepads use this preference pane to give every button and key a job.
Ukelele
SIL's layout editor, for anyone who wants a whole custom keyboard layout rather than a handful of swapped keys.
Apps that make keys do more: macros, scripts and mouse-free clicking
Keyboard Maestro
A macro automation app that fires off actions from hotkeys, typed strings and other triggers, for when a remap grows into a workflow.
BetterTouchTool
Customises far more than keys: mouse, trackpad and Touch Bar input too, with hundreds of triggers and actions to wire together.
Hammerspoon
Lua scripting bridge into macOS; if you'd rather write code than click through settings, it can catch low-level keyboard and mouse events.
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Keyboard Cowboy
An open-source shortcut utility, hosted on GitHub, that launches apps, scripts and whole workflows from the key combinations you choose.
Homerow
Keyboard-only clicking: labels appear over buttons, links and interface elements so you can hit them without reaching for the mouse.
Where remapping breaks
- Password fields. macOS blocks third-party remapping inside secure text fields, so your custom keys stop working while you type a password. That's a system limit, not a bug in your app.
- Big macOS updates. Low-level remappers hook deep into the system, which is why one of the open-source ones here publishes a separate download for each macOS version, back to El Capitan. Check for an update before you upgrade the operating system.
- Permissions. macOS keeps a list of apps allowed to monitor your keyboard, mouse and trackpad under System Settings, Privacy & Security, Input Monitoring, and each has an on or off switch. If a remap silently stops after an update, check its switch there first.
- Two tools fighting. Run one remapper, not two. A macro app on top is fine, but two apps rewriting the same key gives you strange, intermittent results.
- Apple's own hardware. One of the device tools here deliberately leaves Apple mice, trackpads and keyboards alone, so check before buying it for a Magic Keyboard.
A worked example: the hyper key
If you only make one change, make this one. A hyper key is a single key that presses Command, Control, Option and Shift together. Hardly any app uses all four at once for its own shortcuts, so the combinations you build on top of it are yours and rarely clash.
- Turn caps lock into hyper with a remapper. You'll rarely miss caps lock, and it sits right under your little finger.
- Give your five most-used apps a letter each: hyper plus B for the browser, hyper plus M for mail, hyper plus N for notes. Set those in a shortcut or macro app, or a launcher you already use.
- Add window moves next. Hyper plus the arrow keys to snap windows left, right and full screen is the change you'll notice fastest; a Mac window manager can take those shortcuts.
- Live with it for a week before adding more. Shortcuts you don't use by day seven never stick.
If your remapper supports tap-versus-hold rules, you can have caps lock send Escape on a quick tap and act as hyper when held.
What these apps cost
Five of the nine cost nothing: three are open source and two are free, one of them under a freeware licence with open source planned. Three more let you try before buying a licence, and the ninth didn't state its terms on its own site. Only one of the licensed apps prints a figure, and it's a one-off payment under $40 rather than a subscription, so expect tens of dollars, not a monthly bill, if you go paid. You're choosing on fit, not budget. Where you'll spend more is time: a scripting bridge can eat a weekend, while a single-purpose hyper key app takes two minutes.
Do you make Mac apps that remap keys, buttons or shortcuts? Tool makers can ask to be considered for a featured place on this list.
Which kind of app to pick
If you want caps lock as Control and nothing else, use the built-in Modifier Keys setting and stop there. If you want a hyper key and no fuss, a single-purpose menu bar app is the lightest choice. Want tap-and-hold tricks, Escape on caps lock that survives a restart, or different rules per app? You need a full remapper, and if your mouse and trackpad need the same treatment, pick one app that covers all three rather than stacking two.
If what you're after is shortcuts that do things, such as opening apps, pasting snippets or running a sequence, choose a macro or shortcut app; for pure snippets a text expander may be all you need. If you've got a third-party mouse with spare buttons, you want a device tool. And if you'd rather type code than click settings, a scripting bridge will do things no other app on this list can.
Several of these live in the menu bar, so if yours is already crowded, our pick of the best Mac menu bar apps includes tools for tidying it.
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