Apple has admitted it slows down some older iPhone handsets in order to protect the ageing battery.
The technology giant confirmed it introduced a feature to its iOS operating system last year which manages performance on the iPhone 6, 6s and SE to help preserve battery life, which it says diminishes over time.
Many social media users have long speculated that the firm limits older devices to encourage users to upgrade, but the company said the feature was used to prolong the life of its products.
"Our goal is to deliver the best experience for customers, which includes overall performance and prolonging the life of their devices," the tech giant said in a statement.
"Lithium-ion batteries become less capable of supplying peak current demands when in cold conditions, have a low battery charge or as they age over time, which can result in the device unexpectedly shutting down to protect its electronic components.
"Last year we released a feature for iPhone 6, iPhone 6s and iPhone SE to smooth out the instantaneous peaks only when needed to prevent the device from unexpectedly shutting down during these conditions.
"We've now extended that feature to iPhone 7 with iOS 11.2, and plan to add support for other products in the future."
The feature was confirmed after an iPhone 6s user posted images of a performance test to web forum Reddit, which showed an increase in their phone's benchmark performance score after the battery had been replaced.
Apple said the feature is only applied in cases of extreme high or low temperatures, low charge or an aged battery, and was designed to protect the internal components of the phone.