iPhone Duo Review: After 3,000 Folds, Here’s What We Found

Summary

The review examines Apple’s first foldable, the iPhone Duo, focusing on its display and hinge durability, software experience, performance, cameras, and whether a foldable offers enough practical benefit over a conventional phone.

Design, screens, and hinge

• The Duo has a 5.4-inch outer display and a 7.6-inch inner display. Its wide, short proportions prioritize video viewing when unfolded, but make the closed phone unusually wide and less comfortable to hold or type on one-handed.
• The reviewer found the crease nearly invisible in most viewing conditions. A scan measured a 48-micron peak-to-valley crease when new. After 3,000 folds, it deepened to 167 microns—worse than one comparison device and roughly on par with another. The reviewer also noticed slight screen flex over the hinge.
• The hinge held the phone open at angles from 15° to 165°. A CT scan and 3D model revealed linked hinges, gears that synchronize both halves, and spring-and-cam mechanisms that provide resistance and support hovering positions. Magnets help keep the phone shut.
• The hinge creates a teardrop-shaped space for the folded display, measured at about 3.85 mm across at its widest point. The phone also has IP68 dust and water resistance, which the review notes is uncommon among foldables.
• Apple’s inner display uses a nano-texture surface and ultra-thin glass (UTG) above and below the display. The texture diffuses reflections, making the crease less conspicuous and giving the screen a paper-like feel, but also makes blacks appear grayer in ambient light.
• Scratch testing found faint marks under a 6H pencil and more visible, touch-detectable marks at 8H. A pressure test found little evidence of pressure at around 15 N. The reviewer says the inner-screen protective layer can be replaced for about $49, or $19 with AppleCare+, citing an Apple executive.
• The inner screen supports Apple Pencil. The reviewer liked its writing feel, though the camera bump makes the phone wobble on a flat surface. A printed base plate improved the experience.

Software and app experience

• Apple uses the outer screen’s unusual D-shaped layout to move controls to the right, leaving more room for content. This can work well in Apple’s own apps, but may be awkward for left-handed users and for third-party apps that have not been adapted.
• The wider inner display can show more information when apps are designed for it—for example, multi-column social feeds, side-by-side shopping details and product photos, or chat lists beside conversations. However, in a test of 25 popular apps, 60% had not yet been updated. Many unoptimized apps simply stretch across the larger screen without showing more useful content.
• Split-screen multitasking supports dragging content between apps and placing apps side by side or vertically. Limitations include an apparently draggable divider that cannot resize the apps and a keyboard that can squeeze video in vertical split-screen.
• Apple’s unfolding animation aims to keep content in place as the screen opens. The reviewer found that third-party apps—and even some Apple apps—can fail to keep the two screens synchronized.
• Book mode and laptop-style mode offer additional ways to use the folded phone, but the reviewer found them of limited practical value or constrained by the available screen space.

Performance, battery, charging, and cameras

• The Duo and the iPhone 18 Pro models share the A20 Pro chip. CPU results were similar, but the Duo scored about 10% lower in GPU testing. In a 30-minute Death Stranding test, it averaged 33 fps, compared with over 40 fps on the Pro models.
• The Duo reached 46.5°C in the test and reduced screen brightness more than the Pro Max. The review attributes the performance gap and heat to limited cooling space and difficulty moving heat across the phone’s two halves.
• With Apple’s 40 W adapter, charging from empty to full took 1 hour 40 minutes unfolded and 1 hour 52 minutes folded. The phone peaked at 32 W with that adapter, while standard 65–45 W USB-PD chargers reportedly reached 42 W. A 30 W PD charger took 1 hour 43 minutes to charge it unfolded.
• In the review’s heavy-use battery test, the Duo lasted 5 hours 29 minutes—longer than the Air and iPhone 18 Pro, but less than the Pro Max. The reviewer expects it to last a full day with ordinary use.
• In good light, photos looked similar to those from the iPhone 18 Pro, while low-light shots showed more sharpening and smeared detail. The reviewer judged the camera hardware to be closer to the standard iPhone range than to the Pro models.
• The under-display selfie camera produced smeared detail compared with the iPhone 18 Pro, though the reviewer found the result acceptable without close inspection. Using the outer camera for selfies produced better image quality.
• Foldable-specific camera features include an outer-screen preview for subjects and a “Smart Capture” feature that takes a photo when people are ready. The teleprompter use case was only a developer demonstration, with no app available yet.

Overall assessment

The reviewer credits Apple with several thoughtful design choices: the nano-texture display, flat hinge edges, dual UTG layers, IP68 rating, and screen-transition animations. But the review argues these mostly mitigate problems inherent to foldables rather than eliminate them.

Its central criticism is that foldables face a trade-off between the outer phone screen and the inner tablet-like screen. Improving one can compromise the other, while the extra display and hinge bring ongoing costs in weight, cooling, battery life, performance, camera hardware, and price. The reviewer also argues that inconsistent app support can interrupt everyday use: unfolding does not reliably guarantee a better experience.

The video reports strong early demand for the Duo, with shipping dates moving back after preorders opened, but concludes that popularity does not mean foldables have resolved their basic compromises.

Tests and demonstrations

• Crease-depth scans on new foldables and after 3,000 folds
• Hinge-angle and durability evaluation, including a CT scan and 3D hinge reconstruction
• Pencil-based scratch and screen-pressure tests
• Testing of 25 apps for inner-screen optimization
• Gaming performance, heat, brightness, charging, and battery-life comparisons
• Photo and selfie comparisons with iPhone models

Main speaker/source: An HTX Studio reviewer and test team narrate the review. The video also cites an Apple executive regarding screen-layer replacement pricing and mentions feedback and work-in-progress app builds from developers.