Aesthetically similar to its predecessor, iOS 11, it focuses more on performance than on new features, quality improvements and security updates.

Announced at the company's Worldwide Developers Conference on June 4, 2018, iOS 12 was released to the public on September 17, 2018.

The last update, 12.5.7,[2] was released on January 23, 2023. iOS 12 was introduced by Craig Federighi at the Apple Worldwide Developers Conference keynote address on June 4, 2018.

Performance optimizations were made in order to speed up common tasks across all supported iOS devices.

[11] In January 2018, investors JANA Partners and the California State Teachers' Retirement System had issued a public letter to Apple, calling for them to take additional responsibility for the "unintentional negative consequences" that iPhones may have on younger users, and to seek out new ways to limit these effects.

[21] Control Center is separated from the app switcher on iPad and can be opened with a swipe down on the top right corner.

The status bar has been redesigned, and in addition, iPhone X-style gestures are introduced across all iPads running iOS 12.

[22] In iOS 12, the trackpad mode (which allows the user to freely move the cursor) is enabled by long-pressing the space bar on devices without 3D Touch.

[23] For devices with gesture navigation and no home button (iPhone X and later), users can now force quit applications by swiping up from the bottom of the screen (without having to press and hold on them when in the app switcher).

[28] Messages in iOS 12 introduces a new type of customizable Animoji called "Memoji" which allows a user to create a 3D character of themselves.

[29] In addition, Apple added new text and GIF effects similar to those found on other social media applications.

"[37] The new app design is similar to that of Apple Music, and has been praised for its simplicity in allowing users to easily navigate their book library.

[40] After a rainbow flag emoji with an interdictory sign over it appeared on Twitter, several users accused Apple of encouraging anti-LGBT attitudes.