UltraVNC

UltraVNC is a free VNC server and viewer for Windows, built for help-desk staff, IT departments and anyone who needs to control a Windows PC across a LAN, a VPN or the internet. The UltraVNC download is free for all uses, including commercial ones, and the code is released under the GNU GPL by a small team led by Rudi De Vos and Ludovic Bocquet, who have maintained the project since 2002.

Compared with generic VNC builds, UltraVNC adds Windows-specific features: file transfer, chat, Windows account authentication (MS-Logon), a repeater for machines behind NAT and a customisable Single Click package for ad-hoc support. The 1.8 releases in 2026 brought a noVNC web viewer with TLS, passwords stored in Windows Credential Manager, stronger MS-Logon encryption and a long list of security fixes.

UltraVNC at a glance

What it does

• Shares the Windows console from UltraVNC Server (winvnc.exe), running as a service for unattended access or as an application for the current session.
• Connects with UltraVNC Viewer (vncviewer.exe), which also works with other VNC servers that follow the RFB protocol.
• Transfers files and opens a text chat between technician and user during a session.
• Authenticates with a VNC password or with Windows accounts and groups through MS-Logon; since 1.8.2.3, MS-Logon credentials are protected with X25519 and AES-256-GCM.
• Encrypts the whole session with DSM encryption plugins such as SecureVNC.
• Reaches machines behind NAT through UltraVNC Repeater, or with a reverse connection from the server to a listening viewer.
• Serves a browser-based noVNC viewer with TLS, so a technician can connect without installing a client.
• Asks the user to accept or refuse each incoming connection, and can lock or log off the workstation when the last viewer disconnects.

How IT teams use it

Unattended access to office PCs over VPN

1. Install the server on each PC, register it as a system service (from the setup or the tray icon), and set a VNC password on first run.
2. In Admin Properties, enable “Require MS-Logon” and add the help-desk AD group so technicians log in with their own accounts.
3. Restrict TCP 5900 in Windows Firewall to the VPN or management subnet. Do not forward 5900 from the internet.
4. Connect from UltraVNC Viewer to pc-name or its IP; display 0 means port 5900.

Mass deployment with a standard config

1. Run the setup once interactively and record your choices: UltraVNC_1830_X64_Setup.exe /saveinf="C:deployuvnc.inf".
2. Configure one server and copy its ultravnc.ini.
3. Roll out silently: UltraVNC_1830_X64_Setup.exe /verysilent /loadinf="C:deployuvnc.inf", then copy ultravnc.ini into the install folder. The MSI packages suit Group Policy or Intune instead.
4. To set the password from a script, use the createpassword tool from the UltraVNC site in the folder that holds ultravnc.ini.

Support a PC behind someone else’s router

1. Run UltraVNC Repeater on a host the technician controls; open its server and viewer ports on that host only.
2. On the user’s PC, start the server with an ID: winvnc -id:1234 -connect repeater.example.com -run.
3. From the viewer, connect through the repeater with the same ID:

vncviewer.exe -proxy repeater.example.com:5901 ID:1234

For a one-off session, a reverse connection is simpler: the technician starts the viewer in listening mode (port 5500) and the user runs winvnc -connect technician-ip.

Install and first run

Windows. Use the x64 or x86 setup (EXE or MSI) to match the system; a ZIP of the binaries is also available. Installing the server as a service needs admin rights. In the setup you can pick Viewer only for technician machines. The first run creates ultravnc.ini and prompts for a password if none is set.

Ports and firewall. The server listens on TCP 5900 (display number + 5900) and, when the Java viewer option is enabled, on 5800 for HTTP. A listening viewer uses 5500. Windows Firewall must allow winvnc.exe.

Old systems. Windows XP, Vista and Server 2003/2008 need the older 1.2.3.1 release listed on the official site; the current build starts at Windows 7.

macOS and Linux. There is no UltraVNC server or native viewer for them. Mac and Linux technicians can connect to an UltraVNC server with any RFB-compatible viewer, without UltraVNC extras such as file transfer, or use the noVNC web viewer.

Limitations

• Windows only. You cannot run the server on macOS or Linux.
• The classic VNC password is limited to 8 characters, and traffic is not encrypted unless you add a DSM plugin, use the noVNC TLS viewer or run it inside a VPN.
• Exposing port 5900 to the internet is risky; 2026 releases fixed more than ten security issues, including a heap overflow in the viewer, so keep every install updated.
• No cloud relay or address book: you work with IP addresses, a repeater you host yourself, or a separate connection manager.
• Extras such as file transfer, chat and MS-Logon only work between UltraVNC components.

UltraVNC vs alternatives

TightVNC is simpler and also Windows-centred, but it has fewer authentication options and no repeater. TigerVNC is the better choice for Linux desktops and cross-platform viewers. If you want internet access without a VPN or port forwarding, a relay-based tool such as RustDesk is easier to roll out.

FAQ

Is UltraVNC free for commercial use?

Yes. The developers state it is free for all usages, including commercial, under the GNU GPL. Bundling it inside a closed-source installer is not allowed by the GPL.

What is the UltraVNC default password?

There is none. On first run the server asks you to set a VNC password, and you can switch to Windows logins with MS-Logon.

Is there UltraVNC for Mac?

No. A Mac can control an UltraVNC server with any standard VNC viewer, but UltraVNC itself runs only on Windows.

UltraVNC vs TightVNC: which should I use?

UltraVNC has more admin features: MS-Logon, a repeater, encryption plugins and Single Click. TightVNC is lighter and easier for basic LAN use.

What is UltraVNC Repeater?

A small relay program. Server and viewer both connect out to it, so neither side needs inbound port forwarding.

Can I install only the UltraVNC Viewer?

Yes. Choose the Viewer-only option in the setup, or copy vncviewer.exe from the ZIP package; it runs without installation.

Which port does UltraVNC use?

TCP 5900 for viewer connections, 5800 for the optional Java viewer over HTTP and 5500 for reverse connections to a listening viewer.

Last checked against official sources: 1 October 2026 (developer website: uvnc.com). Versions and licence terms change — confirm on the developer's site before deploying in production.