The computing world has mostly moved over to 64-bit systems even though there are still plenty of 32-bit devices around. Apple has already enforced the software upgrade to 64-bit on both macOS and iOS but, due to the legacy baggage it has to support, Microsoft has been slower to cut ties with 32-bit software. Case in point is its own OneDrive sync for Windows which only gets a 64-bit version, albeit one still in preview.
Of course, one can always run 32-bit software on 64-bit computers running 64-bit Windows just as they have always in the past years. The 32-bit OneDrive will continue to work and there are at least two instances where it’s the only option. If you’re on a 32-bit Windows, you naturally can only use 32-bit software anyway but if you’re on an ARM64 device like the Surface Pro X, you’re forced to use the 32-bit OneDrive sync app as well.
For all other situations, Microsoft will recommend using the 64-bit version of OneDrive. It will have better support for large files and have more files stored, mostly because it’ll be running on systems that do support more hardware and hardware-based features.
At the moment, however, this 64-bit OneDrive is still in preview so if you do experience problems, Microsoft suggests downgrading back to the 32-bit version. It all sounds so easy, of course, but since the app deals with files stored on the cloud, some users might be a bit more reluctant to start using the app until it’s labeled as stable.
It is curious how long Microsoft is taking to port one of its core apps to 64-bit, especially on 64-bit ARM which makes up almost all the Windows 10 on ARM devices. Ironically, macOS has long had only a 64-bit version thanks to Apple enforcing that policy on its platforms.