Xiaomi 18 Fold vs. iPhone Duo: Why Do These Foldables Look So Similar?

The foldable smartphone market is heating up fast. The Xiaomi 18 Fold and the iPhone Duo not only launched just two days apart — their chassis dimensions, inner and outer screen aspect ratios, and even their D-shaped display designs are virtually identical. Coincidence, or something more? Based on MKBHD's hands-on comparison of both devices, this article breaks down the supply chain logic behind this foldable face-off and examines where the two products actually differ.

Two Days Apart: Who Copied Whom?

The Xiaomi 18 Fold and iPhone Duo share the exact same body dimensions — same height, same width, matching inner and outer screen aspect ratios, and even the same D-shaped display. What makes this especially intriguing is the timing: the iPhone Duo launched on September 9th, while Xiaomi's foldable debuted two days earlier on September 7th.

The internet quickly split into two camps: one insisting "Apple copied Xiaomi," the other maintaining "Even if Xiaomi launched first, they're still the ones copying Apple." But given that tech product development cycles span months or even years, two nearly identical products arriving almost simultaneously actually follows a very clear supply chain logic.

The real story lies in the tension between secrecy and leaks. Apple is famous for extreme confidentiality — engineers can't even tell their families what they're working on, and product information can stay locked down internally for a long time. But once production ramps up, Apple must engage component suppliers and contract manufacturers, placing orders for foldable OLEDs of specific dimensions, custom-engineered hinges, and precisely sized chassis frames. Those supply chain touchpoints are far less airtight than Apple itself, and that's where information leaks out.

Speed Advantage: How Xiaomi Gets the Jump

It's from these supply chain leaks that the outside world is able to piece together the exact dimensions and form factor of a new iPhone. Software, notably, leaks far less because it doesn't pass through the same supply chain — which is also why Apple can still surprise people with software features.

Manufacturers like Xiaomi may not have Apple's precise CAD renders, but they have enough information to build their own version — and they have a speed advantage. They can move fast and ship a product ahead of Apple's predictable release cadence.

This isn't without precedent. Earlier this year, Samsung teased an ultra-thin phone months before the iPhone Air's September launch — what eventually became the S25 Edge, beating Apple to market with the same playbook. Xiaomi has never shied away from borrowing Apple's design language to attract users, so a foldable that matches Apple's dimensions down to the millimeter is hardly surprising.

Silicon-carbon batteries (Silicon-Carbon Battery) are a next-generation battery technology now widely adopted in Android flagships. The core innovation is incorporating silicon into the traditional graphite anode — silicon can store nearly 10 times more lithium ions than graphite, which significantly increases energy density. In practical terms, you can pack more capacity into the same physical volume, or maintain the same capacity in a thinner, lighter package. This is especially valuable for foldables, where the hinge mechanism already consumes a large chunk of internal space and the chassis is inherently thinner than a slab phone, leaving very little room for the battery. The main challenge with silicon-carbon cells is that silicon expands dramatically during charge and discharge cycles, which can cause electrode cracking and shortened cycle life in early implementations. Xiaomi, OPPO, Samsung, and other Android manufacturers have largely solved these issues at scale. Apple, with its extremely high standards for product consistency and long-term reliability, continues to use traditional graphite-anode batteries — putting it at a measurable disadvantage in volumetric energy density.

Where Xiaomi Pulls Ahead: Weight and Battery

The Xiaomi 18 Fold isn't just imitation — it genuinely outpaces the iPhone Duo on several key fronts.

The iPhone Duo's passport-style form factor feels good in the hand and is easy to hold one-handed, but it's also the heaviest iPhone ever made at 254 grams. That heft will read as premium build quality to many, but for heavy foldable users, a lighter device means significantly less fatigue. The Xiaomi 18 Fold is a full 30 grams lighter — closer to the weight of a standard large-screen slab phone — and the difference is immediately noticeable.

More importantly, Xiaomi manages to fit a 6,000mAh silicon-carbon battery into that lighter frame, with 67W wired fast charging and 50W wireless charging (with an accessory). The iPhone Duo, by contrast, hasn't had its exact battery capacity confirmed, but Apple has historically been conservative on raw battery capacity, using neither silicon-carbon cells nor ultra-fast charging. Estimates put the Duo's combined capacity at around 5,000mAh — potentially less than the 18 Pro Max — and it still has to power a 7.5-inch display. The Samsung Galaxy Z Fold 8 faces the same problem: its 4,800mAh battery drains fast during extended use in the unfolded state. The thinner chassis and hinge-divided interior of foldables make silicon-carbon batteries essentially a perfect fit for the form factor.

Camera Showdown: Triple Lens vs. Dual Lens

Cameras are where the differences are most immediately visible. The iPhone Duo has just two lenses — a main camera and an ultrawide — with no telephoto. The Xiaomi 18 Fold, meanwhile, sports a triple-camera array on the back: a 200MP main sensor, an ultrawide, and a 50MP 3.5x telephoto.

The razor-thin profile of foldables and the way the device folds limit what can fit along the Z-axis — which is also why the iPhone Duo lacks Face ID; there simply isn't enough room, and cramming in a flagship-grade large sensor is equally challenging. That said, Xiaomi at least wins on paper. The iPhone Duo's main camera is widely expected to use the same module as the iPhone 17E — a 48MP sensor with autofocus pixels — at 1/2.55 inches, notably smaller than Xiaomi's 1/1.56-inch, 200MP sensor. Real-world image quality will have to wait for full reviews, but the telephoto category is already Xiaomi's to lose. As a bonus, the camera bar on Xiaomi's back panel doubles as a convenient grip when shooting in portrait orientation.

On the inner display, Apple hides the selfie camera under the screen, while Xiaomi uses a standard punch-hole in the corner. The under-display approach delivers a crease-free, hole-free, iPad-like full canvas, but a corner punch-hole is unobtrusive enough. On crease visibility, Xiaomi falls slightly behind — the inner screen lacks an anti-glare coating and can catch the light — though it's nowhere near deal-breaking. If the Duo and Find N6 are a 9 out of 10 on crease concealment, Xiaomi is around a 7.

Under-Display Camera (UDC) technology hides the selfie camera beneath the display panel by reducing pixel density in that region or using a specially transparent material so light can reach the image sensor. In an ideal scenario, this enables a truly full-screen experience. Current implementations, however, face two persistent challenges: limited light transmission reduces selfie image quality compared to conventional front cameras, and the lower pixel density in that zone can create a visible irregularity when displaying solid colors or bright content. Samsung introduced UDC starting with the Galaxy Z Fold 3 and has improved it meaningfully with each generation, though it still isn't completely invisible. Apple's choice to use UDC on the iPhone Duo — rather than maintaining a notch or pill cutout as it does for Face ID — reflects a deliberate call on user experience priorities in the foldable form factor.

Software Differences: Animations, Multitasking, and the Details

Software is where leaks are fewest and where real differentiation lives. The iPhone Duo's glass-like transition animations when opening and closing the device are genuinely stunning — everything feels fluid and immediately responsive. Android foldables have had open/close animations for years, but the underlying behavior differs: Android defaults to treating a closed lid as the end of a session, requiring you to actively wake the outer screen to continue; the iPhone lights up the outer display when the device is only halfway closed, keeping the animation experience seamlessly continuous.

That said, Android maintains a lead in two areas. First, multitasking: the iPhone Duo supports only two apps side by side, while Android foldables have long offered multi-window layouts, bubble windows, floating windows, and even three apps simultaneously. Second, there's a clever detail that Mr. Mobile has highlighted multiple times — when using the rear cameras as a selfie mirror, Android foldables automatically disable the back screen to prevent accidental touches. The iPhone Duo, as of now, doesn't appear to have this mechanism. Whether these software gaps get addressed in future updates will be worth watching.

At its core, this foldable face-off is a story of differentiation in an era when supply chains make hardware convergence almost inevitable. Dimensions can be "borrowed," but battery life, camera versatility, and software experience are where manufacturers actually set themselves apart.