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. It doesn’t sync file names, directory structure, sharing permission, 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 in instances where 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?

Dropbox LAN sync uses UDP port 17500 for discovery and a TCP port between 17599 and 17609 (exclusive) for data transfer (the first one available).

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 traverse 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. If the network admin configures firewall rules within a broadcast domain or subnet, then Dropbox is bound by those rules. Note: When using local firewalls, like Windows Firewall, Dropbox needs to be granted permission.

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 Dec 18, 2024

The information in this article applies to all Dropbox users, unless otherwise stated.

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.

A LAN is more likely to be used between many devices in an office setting than between few devices in a home setting. 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 the Dropbox icon in your taskbar.
Note: If you don’t see it in the row of icons, click the arrow to see if it’s in the overflow area.
Click your avatar (profile picture or initials) in the upper right.
Click Preferences.
Click the Bandwidth tab.
Check the box next to Enable LAN sync.