How to enable LAN sync

Q: How does LAN sync work?

Dropbox LAN sync allows Dropbox desktop users to discover other Dropbox users on the same network via UDP broadcast, and then form a secure HTTPS connection directly to these other clients in order to transfer data directly, subject to the same strict access controls as the Dropbox servers.

Q: Does LAN sync common folders across different accounts?

Yes. LAN sync works across two separate accounts that have shared folders between them. It only syncs file contents —not file names, directory structure, sharing permissions, or other information.

Q: How does LAN sync find other users and shared folders?

Dropbox LAN sync uses UDP “broadcast” packets that each client sends out on a regular interval, advertising some information about which user accounts and shared folders that client has locally (without sharing any private information, like the name of the shared folder). Other clients on the same LAN can look for this broadcast packet, and use that information to determine which clients they should contact if they want to download data contained in that shared folder.

Q: Is the transfer between users that use LAN sync encrypted?

Yes. Users form an encrypted HTTPS connection between them, using credentials that are unique to the account or shared folder in which data is being transferred. These credentials are issued by Dropbox, and only given to users that have legitimate access to the account or shared folder. The credentials are rotated on a regular basis, including when someone is removed from the shared folder.

Q: What kind of network connection does LAN sync use?

LAN sync uses IPv4. If your network only supports IPv6, then you can’t use LAN sync.

Q: What port does LAN sync use?

<ul><li>UDP port 17500 for discovery</li><li>TCP ports 17599-17609 (the first available) for data transfer</li></ul>

Q: Does LAN sync use mDNS?

No. LAN sync uses a custom UDP-broadcast protocol for discovery, which is unrelated to mDNS.

Q: How does LAN sync work with firewalls?

LAN sync only works within a single UDP broadcast domain. For most users, this will be a single router or smaller, depending on how your router is configured.<ul><li>If the admin sets firewall rules inside that domain, Dropbox is bound by those rules.</li><li>For local firewalls, like Windows Firewall, Dropbox needs permission to run.</li></ul>

Q: Should I have LAN sync always enabled?

We recommend only turning on LAN sync when you need it. If you have it on all the time, it may increase congestion on your local network and cause slower internet connection.

Updated Sep 04, 2025

What is a LAN?

A LAN, or local area network, is a wireless or Ethernet connection between computers and other devices in a specific location.

LANs are more common in offices with many connected devices than in homes with fewer devices. If you’re part of a Dropbox team and you’re not sure whether your computer is connected to a LAN, ask your admin.

What does LAN sync do?

Enabling LAN sync tells Dropbox to use your LAN to sync files that are stored on your LAN, which may speed up syncing for those files.

You can enable LAN sync in your Dropbox desktop app preferences, see below for step-by-step instructions for your device.

Note: If your computer is connected to a LAN, enabling this setting in the Dropbox desktop app will override your bandwidth settings and may speed up syncing for files stored on your LAN.

Not using Dropbox yet? See how Dropbox makes syncing files easy.

How to enable LAN sync in the Dropbox desktop app

Click ☑ Dropbox in the taskbar.
Note: If you don’t see it, click the arrow to see if it’s in the overflow area.
Click your avatar (profile picture or initials) in the bottom-left corner.
Click Preferences.
Click the Network tab.
Toggle LAN Sync on.