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Viewer Gui

UltraVnc Viewer Usage

There are a lot of options that can be configuredfrom the viewer side.
Viewer quick options

Quick options

The quick options relate to the following configurationsettings:

Auto Quick Option: Auto

LAN Quick Option: LAN

Medium Quick Option: Medium

Modem Quick Option: Modem

Slow Quick Option: Slow

Ultra Quick Option: Ultra

View Only
No keyboard or mouse events are sent from the viewer to theserver. The server screen can only be viewed, but notcontrolled.
Auto scaling
The viewer window is automatically scaled to fit the size ofyour local screen.
Use DSM Plugin
Choose a DSM (Data Stream Modification) Plugin and configureit.
To use an encryption plugin, for instance, check this option andselect the plugin in the combo box. The plugin file must be inthe same directory than the vncviewer.exe program. And of course,the same plugin must
be used by the UltraVNC server you connectto.
Specify the repeateraddress here.
Save connection settings as default
If checked, the current settings are saved as default optionsin a configuration file. So next time you run the viewer, youdon't have to reselect all your favorite settings.
Further viewer configuration can be done when pressing theOptions button.

Viewer connection options

Format and Encoding

See Encodings section below.
Note: Grey colors only works with 32 bits color screenresolution. 16/24 bits color resolutions just don't work withgrey colors.
Mouse buttons
Mouse cursor

[0] number of time the reconnect is attempted
0 (default), never reconnect
9 (maximum) 9 time trying reconnect.
gui reconnectnumber only for now.
This is the number of times a reconnect is made before the viewer close the connection.


This section (except Ultra encoding) is taken fromTightVNC'svncviewer man page.

The server supplies information in whatever format is desiredby the client, in order to make the client as easy as possible toimplement. If the client represents itself as able to usemultiple formats, the server will choose one.

Pixel format refers to the representation of anindividual pixel. The most common formats are 24 and 16 bit"true-color" values, and 8-bit "color map" representations, wherean arbitrary map converts the color number to RGB values.

Encoding refers to how a rectangle of pixels are sent(all pixel information in VNC is sent as rectangles). Allrectangles come with a header giving the location and size of therectangle and an encoding type used by the data which follows.These types are listed below.


The raw encoding simply sends width*height pixel values. Allclients are required to support this encoding type. Raw is alsothe fastest when the server and viewer are on the same machine,as the connection speed is essentially infinite and raw encodingminimizes processing time.


The Copy Rectangle encoding is efficient when something isbeing moved; the only data sent is the location of a rectanglefrom which data should be copied to the current location.Copyrect could also be used to efficiently transmit a repeatedpattern.


The Rise-and-Run-length-Encoding is basically a 2D version ofrun-length encoding (RLE). In this encoding, a sequence ofidentical pixels are compressed to a single value and repeatcount. In VNC, this is implemented with a background color, andthen specifications of an arbitrary number of sub rectangles andcolor for each. This is an efficient encoding for large blocks ofconstant color.


This is a minor variation on RRE, using a maximum of 255x255pixel rectangles. This allows for single-byte values to be used,reducing packet size. This is in general more efficient, becausethe savings from sending 1-byte values generally outweighs thelosses from the (relatively rare) cases where very large regionsare painted the same color.


Here, rectangles are split up in to 16x16 tiles, which aresent in a predetermined order. The data within the tiles is senteither raw or as a variant on RRE. Hextile encoding is usuallythe best choice for using in high-speed network environments(e.g. Ethernet local-area networks).


Zlib is a very simple encoding that uses zlib library tocompress raw pixel data. This encoding achieves good compression,but consumes a lot of CPU time. Support for this encoding isprovided for compatibility with VNC servers that might notunderstand Tight encoding which is more efficient than Zlib innearly all real-life situations.


Like Zlib encoding, Tight encoding uses zlib library tocompress the pixel data, but it pre-processes data to maximizecompression ratios, and to minimize CPU usage on compression.Also, JPEG compression may be used to encode color-rich screenareas (see the description of -quality and -nojpeg optionsabove). Tight encoding is usually the best choice forlow-bandwidth network environments (e.g. slow modemconnections).


Experimental, Ultra encoding provides real time performanceover a LAN by utilizing LZO compression. LZO is a datacompression scheme which is suitable for data de-/compression inreal-time. This means it favors speed over compressionratio.

VNCViewer Toolbar




  • Toggle Full Screen Mode

  • Show Connection Options...

  • Refresh Screen

  • Send 'Start' (CTRL+ESC) to host

  • Send Custom Key

  • Show Status Window

  • Close Connection

  • Hide Toolbar Buttons

  • Toggle Remote Input and Remote Blank Monitor

  • Open File Transfer...

  • Select Single Window

  • Select Full Desktop

  • Open Chat...

VNCViewer Context Menu

File Transfer... (Hotkey CTRL+ALT+F7)

Open the file transfer dialog window.

Chat... (Hotkey CTRL+ALT+F8)

Open the chat dialog window.

Show/Hide Toolbar (Hotkey CTRL+ALT+F9)

Show or hide the VNCViewer toolbar.

Disable/Enable Remote Input and Monitor

Disable keyboard and mouse input as well as the monitor onthe remote computer.

Connection options... (Hotkey CTRL+ALT+F6)

Open the connection option dialog window.

Connection info

Open the connection info window.

Request screen refresh

Redraw the screen in VNCViewer. Sometimes the display inVNCViewer misses updates or becomes corrupted. A screen refreshcan then insure that VNCViewer's display and remote computer'sdisplay are in sync.

View only

Disables sending mouse and keyboard events from the VNCViewerto the remote computer.

Various screen size options

Full screen mode (hotkey CTRL+ALT+F12) displays theremote screen on the entire screen of your display.
Together with a hidden toolbar this feels like sitting in frontof the remote computer.
Scaled viewer mode displays the scaled remote screen in a windowwith a user defined size.
Scaled server mode generates less network traffic from serverside and uses a pixel blending algorithm to optimize thedisplay.
Fuzzy screen mode combines Server and Viewer scaling to providereasonable visual comfort and speed even over very slowconnections.
Auto scaling mode scales the view to fit the viewer screen.Normal screen mode (hotkey CTRL+F11) displays theremote screen 1:1.

Full/256 Colors

Change the color depth of the screen.

Send various key combinations

Send CTRL+ALT+DEL (hotkeyCTRL+ALT+F4), CTRL+ESC (this opens thestart menu), CTRL+Key Down, CTRL+KeyUp,
ALT+Key Down or ALT+Key Up.

New connection...

Start a new connection.

Save connection info as... (HotkeyCTRL+ALT+F5)

Save the options and settings of the active connection in afile.

About VNC Viewer...

See version and licensing information of VNCViewer.


Additional Hotkeys

Pressing ALT or CTRL send ALT/CTRL directly to the VNCServer,as if the user selected "CTRL DOWN/CTRL UP/ALT DOWN/ALT UP" fromthe system menu.

When SCROLL-LOCK is activated, all keycombinations (except CTRL+ALT+DEL) are directly sentto the remote computer:

  • Instead of switching applications on the client side,ALT+TAB is sent to the VNCServer.

  • Instead of opening the start menu on the client side,CTRL+ESC is sent to the VNCServer.

  • Instead of opening the system menu on the client side,ALT+SPACE is sent to the VNCServer.

  • Pressing Break/Pause key toggles Full-Screenmode on or off.

  • Pressing PRINT-Screen key requests a full screenupdate (same as selecting "Request Screen Refresh" from thesystem menu)

All the above can be disabled by turning theSCROLL-LOCK key off.

UltraVNC Viewer Commandline Parameters

UltraVNC Viewer Commandline Parameters

-help, -? or -h
Print a help message.
-listen [port]
Start the VNCviewer in listen mode. If port is specified, the viewer listens on that port instead of 5900 default port.
example vncviewer listen non standard port 80
vncviewer.exe -listen 80
-dsmplugin filename.dsm
example1: vncviewer.exe host -dsmplugin msrc4plugin.dsm
example2: vncviewer.exe host -dsmplugin securevncplugin.dsm

-proxy host:port
the proxy is not your office proxy, is ultravnc repeater proxy.

the proxy/repeater mode I (distributor) repeater must be on your lan
"%:\programfiles%\UltraVNC\vncviewer.exe" -proxy host:5901 -connect hostname
"%programfiles%\UltraVNC\vncviewer.exe" -proxy distributor:5901 -connect host -dsmplugin filename.dsm

proxy/repeater mode II (with ID number)
"%:\programfiles%\UltraVNC\vncviewer.exe" -proxy host:5901 ID:1234
"%programfiles%\UltraVNC\vncviewer.exe" -proxy host:5901 ID:1234 -dsmplugin filename.dsm"

Auto  Accept Incoming connection (no SC server info)
server connection set without encryption, there no message is NOT encrypted while vncviewer listen with dsmplugin
-autoreconnect [DelayInSeconds]
-autoreconnect (default value 3 seconds)
example: autoreconnect after 15 seconds
vncviewer.exe -autoreconnect 15 -connect hostname
commandline autoreconnect
value is number of seconds between reconnects This allow to set a bigger timeout between reconnect intervals this function is blocked by repeater for viewer."
%programfiles%\ultravnc\vncviewer.exe" -autoreconnect 30 -connect hostname::5900 -quickoption 3 -dsmplugin SecureVNCPlugin.dsm
-reconnect x (warning) not yet available by command line) only gui
This is the number of times a reconnect is made before the viewer
close the connection.
remove the sponsor of vncviewer message error
-fttimeout sec
Filetransfer timeout sec [1-60]
-keepalive sec
Interval to send a keepalive message
Open a dialogbox on exit " do you realy want to quit"
remove options from system menu ( Filetransfer, chat ....)
Do not send local keyboard or mouse events to the remote computer.
Don't show the status window while connecting.
Do not enable hot keys (like CTRL+ALT+F9 for full screen mode etc.). Can be useful in case of conflict with other installed software hotkeys.
Do not display the toolbar.
Automatically scale the viewer window so that the remote screen fits at best your local screen size.
Display viewer in full screen mode.
Disable auto mode. Required for using the color options below or saving a custom configuration (otherwise the settings from quick options always override).
-8bit, -256colors, -64colors, -8colors, -8greycolors, -4greycolors, -2greycolors
Set the color depth. Fewer colors can significantly reduce the required bandwidth.
Note: Grey colors only work with 32 bits color screen resolution. 16 or 24 bits color resolutions just don't work with grey colors.
Share the server with other viewers, i.e. allow several viewers to connect simultaneously to the server.
Swap left and right button of the mouse.
Do not display any local dot mouse cursor.
Display the local dot mouse cursor.
Display the normal local mouse cursor.
not used
Emulate a 3-button mouse.
Do not emulate a 3-button mouse.
don't change cursor chapes
"." is used as remote cursor
-scale A/B
Scale the display by the factor A/B.
-emulate3timeout Timeout
emulate 3 button mouse with 2 buttons
-emulate3fuzz Emul3Fuzz
emulate 3 button mouse with 2 buttons
Do not transfer clipboard content.
-delay delay
debug option
-loglevel loglevel
Set the loglevel. This can range from 0 (minimal) to 10 (maximum logging).
Open a console window for log output.
-logfile filename
Log to the file specified by filename.
-config filename
Read the configuration from filename.
Record the path to the VNC viewer and the type of the .vnc files in the registry
-encoding encoding
Encoding is either raw, rre, corre, hextile, zlib, zlibhex, tight or ultra. Encodings are described here.
-compresslevel level
Use specified compression level (0..9) for "tight" and "zlib" encodings (Tight encoding specific). Level 1 uses minimum of CPU time and achieves weak compression ratios, while level 9 offers best compression but is slow in terms of CPU time consumption on the server side. Use high levels with very slow network connections, and low levels when working over high-speed LANs. It's not recommended to use compression level 0, reasonable choices start from the level 1.
-quality quality
Use the specified JPEG quality (0..9) for the "tight" encoding (Tight encoding specific). Quality level 0 denotes bad image quality but very impressive compression ratios, while level 9 offers very good image quality at lower compression ratios. Note that the "tight" encoder uses JPEG to encode only those screen areas that look suitable for lossy compression, so quality level 0 does not always mean unacceptable image quality.
-user msuser
ms logon (NTLM1) username set at server (not viewer side)

-password password
Use the specified password for "classic" VNC authentication.
-serverscale scale
Scale the display on the server side by 1/scale. For instance scale = 2 means that the remote screen dimensions are reduced by 2 ("half screen size"), reducing at the same time the amount of graphical data received by a factor 4 (2^2).
-quickoption n
Select a quickoption. Modem option is default
1 = AUTO (auto select best settings, this never use ultra experimental maybe "forever")
2 = LAN (> 1Mbit/s) Max Colors
3 = MEDIUM (> 128Kbit/s )- 256 Colors
4 = MODEM (19K - 128Kbit/s) - 64 Colors
5 = SLOW (< 19Kbit/s) 8 Colors
6 = (custom ?) N/A (not available and fail)
7 = ULTRA (> 2Mbit/s) - Experimental (still experimental after 2 years)

Commandline options are Merged with the default saved settings.
if you save viewonly as default -> a viewer started with a commandline option will always be "viewonly".