Description

aidenbell

opened on Mar 5, 2026

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Bug:

I have a minimal script on Linux with Python 3.14.2 and webui2 2.5.7

Example script

from webui import webui
from webui.webui import Browser

my_window = webui.Window()
my_window.show_browser("http://localhost:8080/", Browser.Firefox)
webui.wait()

Expected behaviour

Firefox based web UI opens and webui.wait() blocks the script.

Actual behaviour

With Firefox installed. The Firefox window correctly displays without the decorations, but the script exits with:

/home/aiden/Workspace/python-webui-test/.venv/lib64/python3.14/site-packages/webui/webui.py:827: UserWarning: The browser you selected might not be installed on your system. if not success: warnings.warn("The browser you selected might not be installed on your system.")

Shortly after a timeout. The Firefox window stays open and displays the correct content.

Activity

1. AlbertShown commented on Mar 5, 2026

   

   AlbertShown

   on Mar 5, 2026

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   I think that's because WebUI waits for the WebSocket connection but it never come in. Can you double check that your HTML is including webui.js ?

   Since you chose to use your own web server instead of WebUI web server, then you may need this:

   Python Script:

   # Set the port that WebUI should use. This means `webui.js` will be available at:
   # http://localhost:YOUR_PORT_NUMBER/webui.js
   my_window.set_port(7070)

   HTML:

   <script src="http://localhost:7070/webui.js"></script>
2. AlbertShown commented on Mar 5, 2026

   

   AlbertShown

   on Mar 5, 2026

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   Just to let you know, in case you chose to use WebUI web server instead, then script will be something like this:

   from webui import webui
   from webui.webui import Browser
   
   my_window = webui.Window()
   my_window.set_root_folder("/home/Foo/Bar/MyWebSiteExample/")
   my_window.show_browser("index.html", Browser.Firefox)
   webui.wait()

   HTML:

   <script src="webui.js"></script>
3. aidenbell commented on Mar 5, 2026

   

   aidenbell

   on Mar 5, 2026

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   Ah this doesn't seem clear from the docs (own issue) that webui.js needs to be required in the browser instance. I was pointing it at a pre-existing Django application that spawned its own webserver.

   I added <script src="webui.js"></script> to the backend's HTML output but the issue persists. Am I right in assuming that webui.js is resolved by some magic, rather than being an actual file needed to be included? I can't find it in the repo.
4. aidenbell commented on Mar 5, 2026

   

   aidenbell

   on Mar 5, 2026

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   Edit, I got it working using the FQ localhost pointing to the webui webserver as suggested above.

   I feel like this could be better documented when "bringing your own webserver" that the webui lib has a webserver spawned for comms with the browser instance. I like the setup though.
5. AlbertShown commented on Mar 6, 2026

   

   AlbertShown

   on Mar 6, 2026

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   Ah this doesn't seem clear from the docs

   We have C own server examples, but not in Python yet, I will create one soon.

   assuming that webui.js is resolved by some magic

   The webui.js is a virtual file get generated by WebUI at runtime to get bindings list securely.

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