Table of Contents


Press CtrlF2 to open the following debug windows

Stepping Execution

Description Action
Run F5
Step execution F6
Pause execution F7
Stop execution F8
Restart F9

The execution of VL can be paused by pressing F7. Pressing F6 repeatedly, causes the execution to make one step at a time. To get back into run mode press F5.

You can also choose to auto-pause whenever an error occurs and jump to the node that threw the exception by activating the Pause on error Setting.


Use IOBoxes connected upstream to display incoming values.

Image:IOBox used to inspect an upstream value


Hover a pin with the mouse to see a tooltip with its name and type.

Image:Tooltip of a pin showing its name and type

If the type is a collection, like Sequence, Spread,... you'll also see the collections number of elements in square brackets and the value of the first three elements in that collection.

Image:Tooltip of a collection type


If you're observing a pin in a patch that is instantiated multiple times there is no way yet to know to which instance this value belongs!


The tooltip shows timings when Show Timings is activated in the Settings.

Image:Tooltip shows timings on nodes

Image:Tooltip shows timings on Datatype definition

Write to Console

The Log window can be opened via Quad > Windows > Log or by pressing CtrlF1.

Use the advanced Write and WriteLine nodes from the System.Console category to write debug infos to the Log.

Pressing the Backspace key with the Console focused clears it.

Warnings and Errors

Image:A node showing an error

Image:A link showing a warning

Image:A pin showing a warning

To get rid of pin-warnings after you've acknowledged them, press CtrlE.

Attaching Visual Studio

In case you encounter errors that are not traceable through techniques mentioned above, you can also attach to your patches with Visual Studio.


Beware, this is not meant for the casual user!

But if you're quite familiar with C# programming, you can do the following:

  • Start vvvv.exe with the --debug commandline argument
  • Run Visual Studio
  • Attach to vvvv.exe
  • Wait for the exception to occur
  • This will bring up the C# code of your patch and jump to the location where the error occured. Here you can also set break points. This may help you figure out the source of the problem.