Joanna Stern put the iPhone Duo hinge through more than 32,000 folds over four nights using a custom machine, and she reported that the phone felt largely unchanged in everyday use. Apple has not published hinge tests or provided a lifetime fold number for the iPhone Duo.
“But in everyday use, I really couldn’t feel a difference. So, after 32,000 folds, it felt pretty much the same as day one, which is pretty darn impressive,” Stern wrote.
A calibrated push-pull gauge used to take readings before and after the Duo fold test showed the hinge was actually stiffer than before. Stern did not comment on whether the fold test made the crease more visible.
Her testing was performed with a case on. The machine opened the Duo flat but did not close it all the way on every cycle. Full details on the machine and how it was built are available in her YouTube video, and she also provides more information in her review writeup.
iPhone Duo hinge test details
The informal stress test ran across four nights and totaled more than 32,000 folds. Readings taken with a calibrated push-pull gauge before and after the run indicated increased stiffness in the hinge, while Stern’s subjective assessment was that she could not feel a meaningful difference in daily use. The test was conducted with a case on, and the machine did not fully close the device on each cycle.
How this stacks up against Samsung’s official tests
Samsung’s foldable displays undergo official durability testing. In 2025, the display used for the Galaxy Z Fold7 passed a 500,000-fold durability test. Samsung Display says that result translates to over 10 years for average users folding about 100 times a day, or over six years for users who fold their device more than 200 times daily.
Until Apple publishes information on display and hinge durability, Stern’s informal test is the only publicly available data on the iPhone Duo hinge. It is unlikely to be the last unofficial folding stress test we see in the coming weeks.
