iPhone Duo begins showing signs of wear after 400,000 folds in durability test

Apple’s iPhone Duo has begun showing signs of wear after being folded hundreds of thousands of times in a long-running durability test, with changes to the hinge’s movement and resistance emerging after roughly three weeks of continuous testing.

CNET has been opening and closing Apple’s first foldable iPhone using a custom-built Fold-a-Phone machine since its October 23 launch. After reviewing sensor measurements alongside photos and video, the publication found that changes in how the hinge opens began at approximately 390,000 folds.

Despite the changes, the device has not met CNET’s criteria for a complete failure. The phone can still fold, although its opening motion is no longer behaving exactly as it did at the start of the experiment. The result offers a first indication of mechanical wear in a test that had previously passed 400,000 folds without a major problem.

As we reported earlier this month, CNET has been running its machine around the clock and broadcasting weekday sessions on YouTube, giving viewers a chance to follow the iPhone Duo’s progress in real time.

The machine repeatedly opens and closes the device at a measured pace, completing approximately 20,000 folds per day. CNET also pauses testing periodically to inspect the display, check the hinge and compare its observations with the measurements collected by the machine.

The distinction between signs of wear and outright failure is important. A change in hinge resistance does not necessarily mean the inner display is damaged or that the phone has stopped functioning. It does, however, suggest that repeated folding is beginning to affect the mechanism after a substantial number of cycles.

The findings are particularly relevant given the questions surrounding iPhone Duo durability since launch. Some early owners have reported cracked inner displays near the hinge, and Apple has acknowledged an issue affecting a small number of devices, advising customers experiencing problems to contact AppleCare for a replacement.

CNET’s experiment cannot establish how often those faults might occur in everyday use. Its test involves a single iPhone repeatedly folded under controlled conditions, rather than the combination of dust, drops, pressure and uneven handling a device may encounter over time.

For now, the results show that one iPhone Duo has endured hundreds of thousands of folding cycles before measurable changes appeared in its hinge behavior. CNET intends to continue testing until the phone can no longer fold, leaving the final failure point still to be determined.