iOS 18 could be the biggest software update in iPhone history, Mark Garman says in the subscriber-only Q&A section of his latest Power On newsletter.

He writes, "I have heard that the new operating system is seen internally as being one of the biggest (if not the biggest) iOS updates in the company's history." He also said that he plans to share more specific details about iOS 18 and the planned changes in the future, so expect to learn more in the near future about what makes the update so big.

Speaking of what we know about iOS 18, there are reports that there is a big focus on AI; according to the Financial Times, Apple has made small AI acquisitions, published research papers, and quietly hired staff with AI experience.

Gurman himself has said that he expects iOS 18 to feature generative AI technology, which could theoretically improve the way Siri and the Messages app answer questions and autocomplete sentences; Gurman also said that Apple has been working with Apple Music and other apps across the platform, including Xcode, to explore using generative AI capabilities.

There are also reports that Apple plans to incorporate a more extensive language model into Siri, allowing for more natural conversations when issuing voice commands.

Apple has also announced that it will support Rich Communication Services (RCS), a cross-platform messaging standard, in November 2023, which could also be part of the iOS 18 package. RCS is an MMS or built as an alternative to SMS messages and is used in all modern Android devices, but Apple has been holding off on introducing it for years. This has widened the gulf between the blue and green chat bubbles that existed before, but RCS should help make cross-OS chat work better.

There is currently a lot of speculation about what exactly iOS 18 will do, and Mark Garman has given some good hints. But until the update is officially announced, nothing is known for sure.