Custom Windows Protocol Handler Registration with Python (No Admin Required)

custom-protocol-handler.py

"""
This registers a simple echo protocol handler so that echo://anything_here will
open a command prompt and echo the full URL.

This does not require admin privileges as it writes to HKEY_CURRENT_USER.

Built from the following reference:
https://stackoverflow.com/questions/3964152/how-do-i-create-a-custom-protocol-and-map-it-to-an-application/3964401#3964401
"""

import winreg
import webbrowser

# Base registry path for the echo protocol
ECHO_BASE = r"SOFTWARE\Classes\echo"


def apply_echo_protocol_registry():
    """
    Generates the registry entries to register the echo:// URL protocol handler.
    """
    # [HKEY_CURRENT_USER\SOFTWARE\Classes\echo]
    with winreg.CreateKeyEx(
        winreg.HKEY_CURRENT_USER,
        ECHO_BASE,
        0,
        access=winreg.KEY_SET_VALUE,
    ) as key:
        # "URL Protocol"=""
        winreg.SetValueEx(key, "URL Protocol", 0, winreg.REG_SZ, "")
        # @="Echo Protocol"  (default value)
        winreg.SetValueEx(key, "", 0, winreg.REG_SZ, "Echo Protocol")

    # [HKEY_CURRENT_USER\SOFTWARE\Classes\echo\shell]
    winreg.CreateKeyEx(winreg.HKEY_CURRENT_USER, ECHO_BASE + r"\shell", 0)

    # [HKEY_CURRENT_USER\SOFTWARE\Classes\echo\shell\open]
    winreg.CreateKeyEx(winreg.HKEY_CURRENT_USER, ECHO_BASE + r"\shell\open", 0)

    # [HKEY_CURRENT_USER\SOFTWARE\Classes\echo\shell\open\command]
    with winreg.CreateKeyEx(
        winreg.HKEY_CURRENT_USER,
        ECHO_BASE + r"\shell\open\command",
        0,
        access=winreg.KEY_SET_VALUE,
    ) as key:
        # @="C:\\WINDOWS\\SYSTEM32\\CMD.EXE /Q /C (echo %1) && pause"
        command = r'C:\WINDOWS\SYSTEM32\CMD.EXE /Q /C (echo %1) && pause'
        winreg.SetValueEx(key, "", 0, winreg.REG_SZ, command)


if __name__ == "__main__":
    print("Applying echo:// protocol handler registry entries.")
    apply_echo_protocol_registry()
    print("Opening echo://Hello_World! to test the protocol handler.")
    webbrowser.open("echo://Hello_World!")