In its endless quest to produce an iPhone that has even fewer physical features than the last, Apple made its iconic home button virtual in 2016, then killed it entirely last year. This is not necessarily a bad thing. Buttons are an ingress point for water (among other liquids) and dust, and internal water damage is nigh impossible to repair. Buttons are also a moving part, and fewer moving parts means fewer potential points of failure.

One of the most interesting and overlooked parts of Apple’s switch from familiar to the futuristic, though, is the effort that went into their Taptic Engine. This work helped Apple move away from physical buttons without alienating too many fans, while also making their watches and laptops feel responsive. It’s a remarkable bit of engineering, and a strategic advantage. Yet it retains the company’s emphasis on a simple, effortless user experience. Having watched Apple’s haptics technology advance inside every one of its devices we’ve taken apart, we’re more than a little impressed, and curious where it will lead in the future.

Apple’s Take on Haptic Feedback

The core technology behind the pseudo-button on the iPhone 7 and 8, the Force Touch effect on MacBook trackpads, and 3D Touch on newer iPhones and Apple Watches is haptic feedback. Put simply, haptic feedback recreates the sense of touch or movement in an otherwise immovable or shallow-clicking object, like a button or trackpad. This is accomplished with a vibration motor, emitting controlled bursts of bzzzt as you tap and press. Apple has branded its own vibration motor the Taptic Engine. First introduced in the original Apple Watch in 2014, then brought to the iPhone 6s in 2015, it found its way into Apple’s entire lineup (minus the iPad, for now). Force Touch and 3D Touch are slightly different, but their core function is the same: next-level haptic feedback.

It wasn’t until the iPhone 7 that the Taptic Engine was given a hero’s quest of making a motionless indentation feel like a moving button.

Apple isn’t the first company to try and incorporate haptic feedback to spice up an inanimate slab of glass. As cellphones lost their keypads in the late 00’s, many companies tried to bring that tactile button feel into the future. Blackberry’s first real iPhone competitor, the Storm, had a whole screen that clicked like a button. Motorola’s rokr e8 used haptic feedback to simulate the feel of a button press. Most Android phones (particularly those made before 2014) shipped with a feature called “vibrate on touch” enabled out of the box that vibrates the whole phone every time you touch it.

What makes Apple’s Taptic Engine different from other haptic applications we’ve seen over the years is the precise engineering Apple has put into it, and the precious space they devote to it inside their increasingly tight devices. Given this effort, Apple has come closer than any firm at actually replacing the tactile mechanical buttons some of us might miss.

The buzzes started out small. Between iPhones 4 and 6, Apple went through three different vibration motors before experimenting with their own design in a premature (unbranded) version of the Taptic Engine in the iPhone 6. When Apple debuted the Engine in 2014, the only extra work it had was driving 3D Touch’s subtle haptics. It wasn’t until the iPhone 7 that the Taptic Engine was given a hero’s quest of making a motionless indentation feel like a moving button. Some liked the buzzy button, some really did not, but it was intriguing work, regardless.

What Puts Taptic So Far Ahead

To understand what makes the Taptic Engine special, it’s important to look at what everyone else is doing. Most Android competitors have switched from Eccentric Rotating Mass (ERM) vibration motors to the more efficient, responsive Linear Resonant Actuator (LRA) motors over the last few years—the same general type of motor in Apple’s engine. But most Android phone makers haven’t done near the amount of legwork Apple has to leverage the new motor’s haptic capabilities in their software. The one exception is LG, which has done some commendable haptics work with their V30 and V40 phones.

The vibration motor on the Huawei P30 Pro, a phone released April 2019, is a notably smaller and more simple device than Apple’s Taptic Engine.

So what is Apple doing with its Taptic Engine that makes its phones’ little vibrations feel better than the competition? Some of it is preference and taste, but other factors play into it as well—chief among them being resonance. When the weighted mass inside a vibration motor moves back and forth at just the right speed, the vibration effect produced by the motor is amplified across the whole phone. Modern smartphone vibration motors are designed to operate within their resonant frequencies—hence the name Linear Resonant Actuator—but just because a motor is vibing at its best frequency doesn’t mean the buzz will resonate with the user.

Apple tunes their Taptic Engines to resonant frequencies optimized for quick, precise taps

Different vibration motors resonate at different oscillation frequencies, and depending on the shape, size, and location of a given motor, a different vibration effect is achieved when the weight in the motor moves at the resonant frequency. Variations in size and shape also affect the time it takes for a motor to ramp up to its resonant frequency and then stop, which in turn affects how precisely it can be used within the OS. Apple tunes their Taptic Engines to resonant frequencies optimized for quick, precise taps; and since they are designed in-house, they can pick specific sizes, shapes, and resonant frequencies for each product. In contrast, other smartphone manufacturers are at the mercy of whichever vibration motor manufacturer they happen to be purchasing from.

Most Android manufacturers just don’t have the same capability to vertically integrate hardware and software the way Apple does, which will always give them an advantage in this kind of game. The exception there is Google’s own Pixel phones—which aren’t technically made by Google themselves, but for which Google is especially present in the design and production stages. Pixel phones have actually all shipped with rectangular LRAs, which are capable of more articulate vibration patterns, like the iPhone’s Taptic Engine. But Google hasn’t done as much to incorporate the fancy buzzer into their software, and their haptics API for app developers isn’t nearly as robust as Apple’s. Android owners, for example, cannot set different vibration patterns or intensities for different calls or texts, at least without additional apps.

Software aside, there are other things that make the Taptic Engine unique and more capable than its LRA siblings inside other smartphones. We could pore over each one in excruciating detail, but to be honest, I don’t think the details matter as much as the overarching truth: the Tapic Engine is the king of haptics because Apple cares about haptics more than anyone else in the industry.

Space inside smartphones comes at a premium right now. Every component inside these $1,000 pocket computers is there for a very specific reason. Compare how much valuable internal space Apple has carved out for their Taptic Engine compared to its competitors. Even when the phone model gets bigger (like the iPhone XS Max) the Taptic Engine gets bigger, too.

The Force Touch trackpad in the 2015 Retina MacBook

Why Feedback Matters for the Future

The commitment to haptics is evident across the entire lineup of Apple’s products that buzz. The Apple Watch’s Taptic Engine takes up a good third of the tiny space beneath the Watch screen, eating up what could be space for a bigger battery. The MacBook Pro’s Force Touch trackpad, on the other hand, was born partially of a desire to save space in the razor-thin 2015 MacBook, which reportedly didn’t have enough room to fit a moving trackpad. But Apple’s gambit paid off. Most people who have used a newer MacBook will tell you that using a Force Touch trackpad will spoil you for just about anything else.

Apple’s haptic prowess hasn’t paid dividends in everything it makes, though. Apple’s marketing boss, Phil Schiller, said at the launch of the first 3D Touch iPhones that, “If it’s just a demo feature and a month later nobody is really using it, this is a huge waste of engineering talent.” Unless you’ve got some outlier friends, you probably haven’t heard many iPhone owners rave about 3D Touch. The Verge claims that 3D Touch’s absence from the iPhone XR shows how it’s an unnecessary, cost-adding feature, and TechCrunch readily agrees.

But the future holds many possibilities for a company with a lot of engineering talent looking at haptics. One such future might replace Apple’s problematic keyboards with no actual keys at all, but a keyless keyboard: a touchscreen that detects force, offers feedback, and can be modified on the fly. As noted by AppleInsider, not only would this allow Apple to avoid having to localize keyboard layouts for international buyers, but it could provide folding screens with a reasonable means of input.

An all-touch laptop seems more like a trade-show prototype than a useful product. But then, so did a virtual home button or a trackpad that doesn’t actually click. Don’t be surprised if Apple harnesses its deep interest in little buzzes to make their future products feel more real than you expect.