It was made publicly available on September 16, 2024, as a free software update for supported iOS devices.

[6] It is the direct successor to iOS 17 and was announced alongside iPadOS 18, macOS Sequoia, watchOS 11, visionOS 2, and tvOS 18.

As with SMS, it is designated with green message bubbles and buttons to distinguish it from blue iMessage conversations.

[15] The quote was later cited in an anti-trust lawsuit against Apple Inc. filed by the United States Department of Justice.

[21] This redesign has led to backlash from many users who find it too confusing and is said to be the most controversial change in iOS 18.

[24] A toggle to activate dark mode icons for first-party apps and many third party ones was implemented.

Previous iOS versions arranged icons on a preset grid, but now users can place them anywhere.

[32] With iOS 18.2, users are able to share a link with others or airlines to track the location of AirTags or other accessories in the FindMy app.

[33][34][35] Reports from law informant suggested that a new security feature was added that would reboot iPhones after 72 hours of inactivity to make it harder to hack,[36][37] something that researchers were able to confirm while looking at the code for iOS 18.1.

[38][39] 18.2 allowed app developers like Truecaller to add real-time Caller ID and spam-blocking.