How to downgrade from macOS 26 Tahoe on a new Mac

A colleague recently acquired the latest M4 MacBook Air, and while the hardware impresses, there are some concerns regarding Apple's pricing for RAM and SSD upgrades, especially during this ongoing memory shortage. Despite these issues, most users are expected to enjoy their experience with this laptop. For this particular colleague, it marked their first encounter with macOS 26 Tahoe and its new Liquid Glass design, which represents the most significant software redesign since the introduction of Apple Silicon with macOS 11 Big Sur in 2020. Although some Apple enthusiasts have exaggerated the negative feedback surrounding Liquid Glass, Apple's statistics indicate that adoption rates for iOS 26 are consistent with those from previous years. However, the transition to Liquid Glass has sparked criticism from long-time Mac users, with developers like Jeff Johnson and Norbert Heger noting ongoing issues with Finder and window resizing. Additionally, John Gruber from Daring Fireball has advised users to avoid upgrading. While I typically embrace software redesigns, allowing their quirks to fade into the background, this colleague faced a different dilemma. They were eager to know if downgrading was possible and, if so, how to go about it. The good news is that the answer is generally affirmative. Apple offers guidance scattered across various documentation, and this article aims to consolidate those instructions for new Mac users looking to revert from Tahoe to the more familiar macOS 15 Sequoia. It's important to note that Apple approaches macOS updates differently than iOS updates. For instance, Apple mandates that devices capable of running the latest iOS and iPadOS versions must install these updates to continue receiving security patches. Therefore, if your iPhone or iPad supports iOS or iPadOS 26, it must be updated to remain secure.