Smart Sync and system extensions

Dropbox Smart Sync uses lightweight integrations with the Windows and macOS operating systems to function. These integrations are called minifilter drivers (on Windows) and system extensions (on macOS), and they allow Dropbox to automatically download your files as soon as you open them.

These integrations work much like the drivers you install to use a printer, copier, or external mouse. In this case, these integrations allow the Dropbox Smart Sync feature to work. You won’t see either the system extension or driver unless you use Dropbox Smart Sync.

Sections in this article:

Why do I see a System Extension Blocked message when I install Dropbox?

On macOS 10.13 (High Sierra), you may see a System Extension Blocked prompt when trying to run the Dropbox desktop application for the first time. If you don’t allow access for the system extension, you won’t be able to use Smart Sync.

Enable Smart Sync
Enable Smart Sync

To enable the Dropbox system extension, simply follow the steps that appear on your computer as you’re setting up Dropbox:

  1. In the Enable Smart Sync box, click Continue
  2. In the System Extension Blocked box, click OK.
  3. In the Allow Dropbox in Preferences box, click Open Preferences.
  4. Under the General settings in Security & Privacy, click Allow.
  • Note: You may first need to click the lock icon and sign in to your computer
Allow system integration
Allow system integration

Important notes

  • If you don’t have admin privileges on your computer, you may need to contact IT or another admin to change this setting
  • Dropbox will still work even if you don’t enable the system extension, but you won’t be able to use the Smart Sync feature
  • Smart Sync is only available for certain Dropbox plans

What happens if I don't allow access?

If you don’t allow access for the system extension or driver, you won't be able to use Dropbox Smart Sync. However, the main Dropbox desktop application will still work like normal.

What if I unintentionally denied the system extension? Can I change this later?

If you unintentionally exited out of this process, you can easily allow Dropbox access:

  1. Click the dropbox icon in the system tray or menu bar.
  2. Click the gear icon.
  3. Click Preferences.
  4. Click Enable Smart Sync.
  5. If needed, click the lock icon and sign in to your computer.
  6. Click Privacy.
  7. Under Allow the apps below to control your computer, check the box beside the Dropbox icon.

How do the system extension and driver work?

Use of a system extension or driver is common among many popular systems:

  • Hardware—like your computer’s hard drive, printers, and copiers
  • Filesystems—like those exposed through Server Message Block (SMB)
  • Software—like antivirus or virtualization programs


Dropbox used publicly-available APIs from Apple and Microsoft to write the system extension and driver. No additional admin permissions are required (beyond what Dropbox has always needed to function).

What does the Dropbox system extension actually do?

System extensions enable "callbacks." Callbacks are real-time calls that confirm you have permission to do things like move, delete, or change ownership of files in shared spaces (like a folder). If you don’t have these file access permissions, system extensions allow Dropbox to send warnings when you may be taking an action that could unshare folders or delete shared content.

Security and usage

System extensions and drivers can give applications additional access to your computer’s operating system. Dropbox is cautious in only using these extensions to improve your experience with our app.

Some notes on what we don’t do:

  • We don’t use system extensions to interact with any files other than those stored in your Dropbox
  • We don’t use system extensions to make network requests
  • We don’t use system extensions to parse any data in the filesystem
  • We don’t use system extensions to read or write files

Security and stability

Dropbox takes great measures to protect your data and privacy, and we designed the system extension and driver with security and stability as top priorities. In fact, many of the engineers who wrote this extension previously worked on filesystem technologies at various OS vendors.

These components have gone through extensive security reviews with internal security teams, as well as audits done by external penetration testers. We’ve run these components both internally at Dropbox and in cooperation with enterprise-scale beta customers. In both cases these components ran successfully.


These integrations are core to current and future Dropbox client services. There is no way to disable or opt-out of using the system extension or minifilter driver on the Dropbox desktop client. Doing so would also disable important alerts that prevent users from accidentally deleting shared data, or taking unintended file actions.

If you don’t want to install the Dropbox desktop application, you can view, share, and download your files without the desktop integration by using only the Dropbox website at

Can I choose to not install this extension?

Please note that your privacy and security are of the utmost importance to us. Smart Sync and this component have been subjected to rigorous testing and inspection to ensure stability and security. 

Read more about Dropbox trust and security.

Read our detailed technical blog about Smart Sync and the driver.

Smart Sync is an opt-in feature so you can choose to opt-out if you wish to do so. However, you cannot use Smart Sync without enabling the system extension or driver.

I'm a Professional customer. Can I opt out of the system extension?

Yes. If you use Dropbox Professional, you can opt out of the system extension at any time. However, please note that opting out of the system extension will disable Smart Sync. You must have the system extension enabled to use Smart Sync.

To disable the system extension:

  1. Sign in to
  2. Click your avatar at the top of any page.
  3. Click Settings.
  4. Scroll to Dropbox system extension.
  5. Toggle this setting to off.

Note: This opt-out experience is only available for Dropbox Professional customers.

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