The sticker on the back of the console which states "Warranty void if removed." is actually illegal. According to the Federal Trade Commission (FTC), the sticker violates the 1975 Magnuson-Moss Warranty Act which states that any manufacturer that charges more than $5 for their product cannot put repair restrictions on a device that it offers a warranty for. On April 9th, 2018, the FTC sent a letter to Sony, as well as Nintendo, Microsoft and Apple, who place similar stickers on their consoles and devices, giving them a 30 day warning to change their official warranty policies or face legal action.
The PlayStation 4 cost $381 to build, which is considerably less than compared to the PlayStation 3 which cost $805 to first produce.
Kazuya Sakakihara, a senior software engineer who previously worked for Sony during the creation of the PlayStation 3 and PlayStation 4, left his name within a snippet of code used for the PlayStation 4's hard drive. The location of his name in the code is unusual, as names are often left in a separate part of code data for storing comment data, often in abbreviation or initials. However, in the case of Kazuya Sakakihara, his name is left in full within the middle of the data unencrypted, although with a minor spelling mistake.
Dualshock 3 controllers include a built-in light indicator to be used alongside the Morpheus VR headset. This means that the Morpheus headset was a key component to the design of the controllers, prior to the headset even being announced.
According to President of Sony Computer Entertainment Worldwide, Shuhei Yoshida, some of the features of PlayStation 4 were inspired by Dark Souls and Demon's Souls.
The PlayStation 4 sold over 1 million units on its first day of release in the United States. This was before the console had been released in any other region.