Open a web browser with EXEC node


Hello, I'm attempting to use Node-Red to open a web browser UI on the Windows 10 PC which hosts Node-Red.
I've tried using the EXEC node in spawn mode for this purpose with the command powershell start chrome, however chrome launches as 7 background processes rather than a chrome application with a desktop UI (i.e. no browser UI is visible in Windows).
Node-Red is running under the admin user account, on a single user PC.
My goal is to use Node-Red to open / close Chrome UI, and to control the displayed content.
Any assistance is most appreciated - thanks in advance.


Windows exec Node. start process in the foreground

This may be the issue. Are you saying that you are running it from an elevated command or from a different user to the one normally logged in?

As far as I can tell, you should be able to do this fine. I'll check if I have time.

However, don't get your hopes up too far. You do realise that you cannot automate Chrome from powershell, let along Node-RED don't you?

There are however tools that will let you do that such as Selenium. I think some of the headless browser tools also let you create a window as well.



Node-Red is running under the logged in user account, which is also an administrator account.

I was able to successfully use Selenium to launch Chrome using node-red-contrib-selenium-webdriver.
For comparison purposes, I tried using Node.js Puppeteer via a Function node to launch Chromium. This worked with limited success, as Puppeteer employs asynchronous callbacks which Node-Red doesn't appear to support.
Sadly, while Selenium works, the web site I was using it with relies on user authentication and this appears to be lost, resulting in a manual login each time.

I still don't understand why the EXEC node won't launch chrome under Win 10. I tried launching VLC (start vlc) and observed the same behaviour with the EXEC node, i.e. VLC spawned as a background process without a UI. The same command works successfully when entered to Powershell running under the user account.

I tried using Node-Red running under Raspbian to launch Chromium with no luck. Entering pi@raspberrypi:~ $ chromium-browser & disown into a terminal window works , however the same command used in the EXEC node doesn't.
The following debug messages were received :
[11312:11312:1126/] Failed to put Xlib into threaded mode. and (chromium-browser:11312): Gtk-WARNING **: cannot open display:

There's probably an obvious reason related to the use of a child process in the EXEC node, but my software skills are rather limited.

Thanks for your help.



OK, that is different. Such a user only gets limited access by default, many tasks will generate the protection dialog. Not the same as running Node-RED itself with admin privileges.

Well, NR is written using JavaScript/NodeJS so in theory, it does support them. However, integration can be a challenge. It might need you to require the library in settings.js as a global variable - you can then make use of it from within a function node. A proper custom node would be better of course but a lot more work.

It would be interesting to try the equivalent call direct from a simple, test, Node.JS app. That would probably show whether it is a Node-RED issue or a Node.JS one.

Also, have you tried starting chrome.exe directly from the EXEC node?



So, some quick tests.

Under Windows 10, even with PowerShell set as the default shell, the exec node starts a cmd window not a powershell. It is that that is causing the issue.

Change the exec to be the following command (adjusting for the location of your ps1 file):

powershell -NonInteractive -NoLogo ./data/chrome.ps1

That works just fine.



I tried your suggested fix however the problem remained. So I checked in task manager and Node.js was running as a background process owned by SYSTEM. As it turns out, I am launching node-red via the Windows Task Scheduler and I had selected the 'run whether user is logged on or not' button. After changing the node-red task to run only when the user is logged on, and running the task, Node.js appeared as an application owned by the user. Magically I was now able to launch chrome via the EXEC node using the command path\script.cmd where script.cmd is start chrome "".
The lesson here seems to be don't expect Node.js running as a system service to launch applications with a UI.
Thanks so much for your help.

1 Like


Which is the same for Linux / Pi - as per your "can't open display" messages above.

1 Like


sorry for my poor english.

do you can´t use eletron-node red?



There are lots of ways to run Node-RED, it depends on your requirements. Personally I don't use the Electron version as I don't need it. But I tend to run NR manually on my Windows PC as I use it mainly for development and occasional bits-and-pieces so I don't need it running all the time. I have defined some handy scripts in my npm package.json file. So I have standard ways of updating and running NR and its nodes.