How to Turn Your Mac’s Caps Lock into an Extra Modifier Key

Unless you’re prone to yelling on the Internet, you probably don’t use Caps Lock for much. That’s weird since it’s right next to a bunch of useful modifier keys. Here’s how to make Caps Lock as handy as the others.

What Can You Do With an Extra Modifier Key?

Perhaps the coolest thing to do is bind fully custom hotkeys. With the use of an app like BetterTouchTool, you can use an extra modifier key to add an empty slate of hotkeys to which you can attach actions. If you want to trigger a shell script or open a new email tab whenever you press Caps+B, you can do that.

You can do the same custom hotkeys without Caps Lock, but you’ll be stuck pressing weird combinations like Shift+Control+Command to not interfere with default shortcuts. With this method, any app that allows you to set your own hotkeys will support the new Caps Lock modifier.

You can also rebind existing shortcuts to use Caps Lock. If there’s an overly complicated shortcut that’s bugging you, you can rebind it in macOS’s keyboard settings to make it easier to press. For example, the hotkey in macOS to take a screenshot of a selection is Shift+Command+5, but you could rebind it to Caps+S.

Repurpose Caps Lock With Karabiner

Now, there’s no way to emulate an extra modifier key properly, so for compatibility reasons, a better way to get this functionality is to remap Caps Lock to act like you’re pressing the Shift, Control, Option, and Command keys at the same time. Since this is such an absurd combination, no app is going to require you to press every one of them for a hotkey, and there should be no interference.

This does mean you’ll lose out on combinations such as Caps Lock+Command, but it should work simply enough with any other alphanumeric key. You can remap Caps Lock to an extra function key, like the F13-20 keys, but it may not work as a hotkey in every app. You can also natively remap the Caps Lock key to Escape (or any other modifier key), but this doesn’t add any extra functionality; it just relocates the key.

The app we’ll use to rebind Caps Lock is Karabiner, a free keyboard remapping tool for macOS. Download and install the app, and open the preferences. Under the “Complex Modifications” tab, add a new rule with the button at the bottom.

Usually, with Karabiner, you’ll have to edit the JSON for your new rule and add it manually. But one of the examples it comes with is exactly what we’re trying to do, so you don’t have to do any additional setup. Just click “+ Enable” next to “Change caps_lock to command+control+option+shift” to add the rule to Karabiner.

You’ll want to make sure Caps Lock is turned off before adding the rule, or you’ll be stuck YELLING FOREVER. You can always turn the rule off to toggle Caps Lock in the future, but this particular rule doesn’t have a way to use the key in any other way.

If you want to fix this, you can click “import more rules from the Internet” and download the “Change caps_lock” set from the official page.

You’ll see a new category of rules, and there’s one that will let you use Shift+Caps Lock as a regular Caps Lock key. You can enable this one and remove the old one to replace it.

A True Hyper Key

The Capslock Enhancement ruleset deserves mention here. While remapping Caps Lock to every other modifier provides a clean slate for new hotkeys, this ruleset finds a use for each key. By default, it stills maps to every modifier like the previous method but has a few categories of hotkeys enabled on top of that, so you can disable individual sections you don’t like to give you some space for customization.

You can import it the same way you’d import any other rule to Karabiner, or you can visit the install URL in your browser and choose to open it in Karabiner.