Apple's next-generation AI dictation feature for the iPhone 17 Pro and iPhone Air is not turned on by default in the first developer beta of iOS 27.

Apple says the new AI-powered dictation system delivers "a major boost in accuracy," with more reliable on-the-fly capitalization and punctuation than the existing dictation system. The feature runs on Apple's new AFM 3 Core Advanced model, which is a 20-billion-parameter, natively multimodal system that uses a sparse architecture, activating just one to four billion parameters at a time depending on the request.

To fit a model that large onto a smartphone, the full model is stored in flash memory rather than DRAM, with a lightweight routing block selecting a fixed set of "experts" during initial processing and periodically reselecting them during generation, a technique Apple calls Instruction-Following Pruning.

In side-by-side human evaluations against Apple's previous production dictation system across seven quality dimensions, AFM 3 Core Advanced was preferred on overall quality by a margin of 44.7% to 17.6%, with that preference holding consistently across the other six dimensions, which include punctuation, casing, layout, meaning capture, disfluency handling, and style.

Because of the model's size, the upgraded dictation is limited to a handful of newer devices: the ‌iPhone 17 Pro‌ and ‌iPhone 17 Pro‌ Max, the ‌iPhone Air‌, the Vision Pro with M5 chip, iPads with an M4 chip or later with at least 12GB of RAM, and Macs with an M3 chip or later with at least 12GB of RAM. Notably, the standard iPhone 17 is excluded, as it ships with 8GB of RAM rather than the 12GB the larger model requires. The same AFM Core Advanced model also powers Apple's new customizable expressive Siri voices, another opt-in preview as of beta 1.

The new dictation model runs entirely on-device, so transcription quality stays the same whether or not the iPhone is connected to a network. It remains unclear whether the preview will stay off by default when ‌iOS 27‌ is released officially later this year, or whether Apple will switch it on automatically at some point during the beta cycle this summer.