App developers need to be poised for a redesign because Apple's iPhone is getting bigger.
The tech giant will roll out the iPhone 6 in two sizes - 4.7 inch and 5.5 inch - in September, according to industry insiders who have seen the prototypes.
The new iPhone screen will be made entirely from scratch-resistant sapphire crystal glass, they said. Sapphire crystal, second to diamond as the hardest material, is now used by Apple for its iPhone camera lens cover and touch identification.
It will also sport a new display at 441 pixels per inch (ppi), the same as the Samsung Galaxy S4. The highest definition Apple now offers has only 326 ppi.
"They have to tackle the phablet [devices that serve as both phone and tablet] market. People want bigger screens now," one insider said.
The iPhone 5S, Apple's largest phone at 4 inches, is notably smaller than the S4, which measures 5 inches, and the Galaxy Note 3, with a 5.7 inch screen.
Last week, Apple repurchased US$14 billion worth of its stock after announcing disappointing first-quarter results.
The company originally said it intentionally kept the screens small to fit comfortably in a user's hand. Since then, the iPhone 5C has suffered poor sales numbers, its competitors have more or less all upgraded to larger devices, and China, the world's largest smartphone market, has been rapidly snatching up Samsung phones.
According to the two insiders, the 5C will be gone while the 5S will stay but be made from cheaper material.
Despite widely circulated rumours that the new phone will be curved, insiders say the iPhone 6 will have a flat screen.
"The screens will be flat. Apple doesn't do anything until Samsung does it, and then they improve upon it," another insider said.
The arrival of sapphire means a dramatic increase in the cost of making an iPhone, as sapphire is far more expensive than the present Gorilla Glass, but it remains unknown whether the price of a single iPhone will go up.
The design "freeze" for the iPhone 6 - after which no changes will be made - is set for April this year, they said.