macOS future strategy

[richardlau]

Currently the project builds three macOS packages available to download from nodejs.org:

• macOS arm64 tarball
• macOS x64 tarball
• macOS universal binary pkg (i.e. the same installer installs either arm64 or x64).

To build the pkg we build Node.js twice on an arm64 macOS VM:

• Once for x64 under Rosetta 2
• Once for arm64 (native)

and then combine the two into the pkg, sign/notarize.

Apple have announced that the last release of macOS that will support Rosetta 2 will be macOS 27. That's the version two on from what we're currently on (macOS 15 -- Apple renumbered so the sequence goes macOS 15, macOS 26, macOS 27). The same Apple announcement said that the last macOS version to support x64 is Tahoe (26).

So we have two decisions:

1. At some point we make the pkg builds arm64 only (as we currently need Rosetta 2 to build those without significant rework of how the releases are done).
2. At some point we will need to drop the x64 macOS version of Node.js completely.

Planning is a little difficult with macOS because Apple do not usually announce End-of-Life dates... they just stop releasing after a while. Also they have made changes before around signing/gatekeeper which forced Xcode updates that in turn forced macOS version updates. So there's a large element of "our best guess" when trying to work out what we're likely to be able to support for the duration of a Node.js release line.

Starting the discussion now as I think our preference would be to make changes on semver major boundaries (unless Apple forces our hand as with the previously mentioned signing/gatekeeper change). So discuss first wrt. Node.js 27 (2027) and if we decide that is too soon, switch focus to Node.js 28 etc.

Refs: nodejs/node#63055

[sxa]

Summary of some points from the other issue:

• We currently have downloads broken down by OS and architecture but not the OS+arch pipeline so we do not know what split of tarball downloads we have on macos/x64 vs macos/arm64. Can we look at getting that information for the purposes of getting trend data as we head towards v27?
• For other downloads, I had a quick look at brew and they do not publish an architecture breakdown on https://formulae.brew.sh/formula/node but we could potentially ask if that information is available as I expect that accounts for a significant source of macos downloads.
• We should consider what to do if there are likely to be a "significant" (definition open to interpretation) number of downloads still occurring when macos 26 goes out of support. As to Matteo's comment we may not be able to have securely patched servers (But we should consider that ours are exclusively dynamically provisioned machines from Orka) and we could potentially still build and test under macos on arm64 machines under Rosetta if required for longer than the macos26 timeframe.
• For other platforms downgraded to the experimental category, such as 32-bit arm and x86, we had the ability to downgrade them while building as part of the unofficial-builds project for anyone who chose to stick with them for a transitional period. Due to the nature of the unofficial builds server - which is a Linux host - such a process may be harder to achieve with macos (technically we had Windows/arm64 distributed on the unofficial-builds server for a while but that was a manual process).
• We should also bear in mind that we can downgrade macos/x64 to experimental status and not actively distribute it through the main release channels while still testing in the CI for some period. This would be consistent with the current situation that Alpine/musl builds are currently in.

[sxa]

As another data point to give an idea of the relative use of the two architectures, another major language runtime (Eclipse Temurin by Adoptium) currently has around 8X more macos tarball/package downloads of the JDK on arm64 when compared with x64. For older releases like java 11 it's about 3X, although for the JRE instead of the JDK the numbers are much closer (in fact for java 11 the JRE has more x64 downloads than arm64). JRE/11 vs JDK/25 are shown in the charts below: