OneDrive for Mac Gets a Native Sync Engine and Doubles Its Speed

Microsoft has rebuilt OneDrive’s Mac client from the inside out, cutting sync times by up to half and stripping out a hidden folder that has dogged the app since 2022. Version 26.098, built around what Microsoft calls the Native Sync Engine, started rolling out to Microsoft 365 Insiders on June 10.

The rebuild fixes a problem Microsoft created for itself. Back in 2022, engineers bridged an old sync engine to Apple’s file system rules with a mirrored cache folder, a shortcut that quietly caused years of disk space and reliability complaints. The new engine is Insiders-only for now, and it arrives the same month Microsoft confirmed it will kill document editing in Office 2019 for Mac over expiring certificates, pushing more users toward a subscription.

A Native Engine Doubles Sync Speed on Mac

Microsoft says the numbers are real, not marketing gloss. In its own performance testing, the new system is about 2x faster for initial sync and on-disk state changes compared with the old client. It also draws less CPU, less memory, and less battery.

The company frames this as the biggest architectural change to OneDrive on macOS since it adopted Apple’s File Provider platform four years ago. File Provider is the system Apple built so cloud storage apps can show files in Finder without keeping full copies on disk at all times. Meeting its rules forced OneDrive’s engineers to rethink how the app touches the file system, rather than patch the existing code again.

Folder browsing gets a practical upgrade too. Files used to materialize on disk only the first time a folder was opened, which meant Finder sometimes sat on a loading screen while apps waited for content to appear. Under the new engine, every file and folder is always browsable on disk, so navigating OneDrive is supposed to feel like navigating any other folder on the Mac.

What Still Lives in That Hidden Folder

The hidden folder is not gone. It is just doing far less work. Under the new engine, it holds metadata only, with a short list of exceptions where actual file data still passes through it temporarily:

• Unsynced changes – files you have created or edited that have not yet finished uploading; the copy disappears once the upload completes.
• Link file types – OneNote shortcuts and similar files, typically a few hundred bytes, kept indefinitely because of how they work.
• Certain macOS packages – GarageBand projects, app bundles, and some older iWork files, which are retained longer than ordinary documents.

Microsoft says the practical effect is a folder that barely registers on a drive. For a consumer account with roughly 10,000 items all available locally, the metadata folder uses only a sliver of storage. That is a sharp contrast with the old design, where the hidden cache mirrored entire file trees and could balloon large enough to fill a laptop’s disk on its own, according to complaints logged for years on Microsoft’s own support forums.

The 2022 Workaround That Aged Badly

Every reliability complaint traces back to one decision. When OneDrive moved to File Provider in 2022, Microsoft needed the existing sync engine to keep working without a full rewrite. Microsoft had already begun modernizing the Mac app earlier this year with a redesigned Activity Center and native system dialogs, but the sync engine underneath stayed untouched until now.

The mirrored cache solved that immediate problem and unlocked features like Known Folder Move. It also became, in Microsoft’s own words, the root cause of most of the reliability and performance issues Mac users reported for the next four years. The company spent that time rebuilding large portions of its code rather than patching the old approach again.

Microsoft did not undersell its own fix in the announcement.

The Native Sync Engine provides the fastest, most reliable experience we’ve ever delivered on the Mac.

Microsoft’s OneDrive team wrote that line in the June 10 blog post announcing the rollout, adding that the rebuild eliminates entire classes of errors baked into the old bridge architecture.

How Do You Know If You Have It?

Open OneDrive’s preferences on a Mac, click the About tab, and check the version suffix. If it ends in a value such as (26K), the Native Sync Engine is already running. Any other suffix means the Mac is still on the legacy client, and nothing changes until Microsoft’s staged rollout reaches that device.

Joining is optional and manual for now. Anyone not already enrolled can open OneDrive preferences, go to About, and check the box to join the Insiders program to get the update early. Microsoft warns the upgrade itself takes a couple of minutes, with File Provider needing a little longer to catch up, though the app stays usable the whole time.

Enterprise rollouts follow a more structured path. Microsoft ships sync client updates through Insiders, Production, and Deferred rings, and Insiders and Production both refresh weekly while Deferred updates roughly every two months, giving IT teams a buffer before a change reaches business-critical machines. That staged approach echoes how Microsoft has handled other default-on changes across Microsoft 365, including its recent decision to auto-install Copilot for many tenants and leave admins to adjust the defaults after the fact.

What we know:

• Confirmed: Version 26.098 and the Native Sync Engine began rolling out to Insiders on June 10, cutting initial sync and on-disk state changes by up to half.
• Confirmed: The hidden cache folder now stores metadata only, with external drive support added for the first time.
• Unconfirmed: Microsoft has not said when the Native Sync Engine reaches the Production or Deferred rings most business users run.
• Unconfirmed: Whether Mac will get the same 1 million item sync ceiling Windows is previewing on the same timeline remains unstated.

A Bigger Push Toward Microsoft 365 Follows

The timing works against Microsoft’s own good news. Days after touting faster, lighter OneDrive syncing, the company confirmed it will end document editing in Office 2019 for Mac because underlying security certificates are expiring. Anyone still on that older, one-time purchase suite will need to find another editor or move to a Microsoft 365 subscription.

OneDrive itself is also becoming less of a plain file store. Microsoft has been layering Copilot, its AI assistant, directly into Finder and the Activity Center so licensed users can summarize documents or ask questions about files without leaving the desktop. That push has already drawn scrutiny: a Copilot-powered rename feature in OneDrive reads the contents of uploaded files to suggest better names, a detail some users only discover after the fact.

The Native Sync Engine is also described internally as the foundation for something bigger. Microsoft’s OneDrive team told attendees at a May customer session that the same rebuild underpins a coming ability to sync up to 1 million items in a single library, a feature already in public preview on Windows. Mac has no matching date yet. For now, the fix that took four years to arrive is still a few weeks from finishing its first, smallest rollout ring.

Frequently Asked Questions

What Is Microsoft’s Native Sync Engine for OneDrive on Mac?

It is a ground-up rebuild of how OneDrive talks to macOS, released as version 26.098. Microsoft says it removes the mirrored cache folder used since 2022, doubles initial sync speed, and lowers CPU, memory, and battery use, and it is also described as the base for a future 1 million item sync limit already previewing on Windows.

Will I Lose Files When the Update Installs?

No. Files already synced stay exactly where they are in the OneDrive folder. The upgrade itself takes a couple of minutes, and File Provider needs a little longer to finish behind the scenes, but Microsoft says the OneDrive folder remains usable throughout the entire process.

Does This Update Apply to OneDrive on Windows Too?

No, the Native Sync Engine is Mac-specific. Windows is getting a related but separate upgrade instead: support for syncing up to 1 million items in a single library, which Microsoft moved into public preview separately from this Mac release.

When Will the Update Reach Everyone, Not Just Insiders?

Microsoft has not given a date. The company says the Insiders rollout alone will take several weeks to reach that entire audience, and it has declined to say when the Native Sync Engine will reach the Production channel that most non-Insider users run.

Can I Move My OneDrive Folder to an External Drive Now?

Yes, if the Mac and the external drive meet Microsoft’s requirements. The Native Sync Engine places both the synced files and the metadata folder on that drive. On older macOS versions or drives that do not qualify, everything falls back to the Mac’s internal home volume instead.