What you’re seeing is:

• Window Title (the standard macOS window title bar, at the top)
• Web Page Title (rendered by the HTML page itself, potentially as a or similar at the top of your actual webpage)

Why it happens On macOS, the underlying Cocoa implementation of pywebview sometimes renders the title as part of the window content as well as in the titlebar, due to the way the NSWindow/NSView components are integrated if not all window management is handled natively by your code.

Proposed fix : Do not set the title using create_window, and set it afterwards

For example :

import webview

def set_my_title(window):
   # window refers to the window object you created
   window.set_title("blah")

window = webview.create_window(
             "",  # empty title set for the webpage
             f"http://localhost:{port}",
             width=1400,
             height=900,
             min_size=(800, 600),
             on_top=False
)

webview.start(set_my_title, window)  # set title here