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A package with basic native messaging apis for webextensions

Project description


A Python package for interfacing with Native Messaging in WebExtensions

See Native Messaging on MDN

Based on Native Messaging on MDN and native-messaging on mdn/webextension-examples (MPL 2.0 License)

pip3 install nativemessaging


nativemessaging.get_message() will poll for a message from the browser.
If runtime.connectNative is used, get_message() must be called repeatedly in a loop to poll for messages.
If runtime.sendNativeMessage is used, get_message() only needs to be called once.

encode_message( message_content )

nativemessaging.encode_message() takes one argument, a message to be encoded.
Returns an encoded version of a message to be returned to the browser. Use with send_message().

send_message( encoded_message )

nativemessaging.send_message() takes one argument, an encoded message from encode_message(). Returns a message to the browser.


Browser side:

function onReceived(response) {

// runtime.connectNative
var port = browser.runtime.connectNative("application_name");

// runtime.sendNativeMessage
browser.runtime.sendNativeMessage("application_name", "hello").then(onReceived);

App side:

import nativemessaging

while True:
    message = nativemessaging.get_message()
    if message == "hello":


nativemessaging-install is a command line script provided with the package.


nativemessaging-install browser [--manifest manifest]

  • browser - positional argument, 1 or more parameters. Must be chrome or firefox.
  • --manifest - a path to a manifest file to use for installing.


A native-manifest.json file is expected in the current working directory when running the script, unless --manifest is passsed. The format must be similar to the native manifest format for Chrome or Firefox, with two main differences:

  • path must be a relative path to the native app in relation to your current working directory.
  • Both allowed_extensions and allowed_origins must be in the manifest to work with both Chrome and Firefox.
    "name": "application_name",
    "description": "description",
    "path": "",
    "type": "stdio",
    "allowed_extensions": ["extension@id"],
    "allowed_origins": ["chrome-extension://extension-id"]

Created files

On Windows, it will create <application_name>_firefox.json and <application_name>_chrome.json in the same directory as <path>.
A batch file will also be created for python apps on Windows.
A registry key is created at HKEY_CURRENT_USER\Software\Google\Chrome\NativeMessagingHosts\<application_name> or HKEY_CURRENT_USER\Software\Mozilla\NativeMessagingHosts\<application_name>

On linux, it will create ~/.config/google-chrome/NativeMessagingHosts/<application_name>.json or ~/.mozilla/native-messaging-hosts/<application_name>.json

On mac, it will create ~/Library/Application Support/Google/Chrome/NativeMessagingHosts/<application_name>.json or ~/Library/Application Support/Mozilla/NativeMessagingHosts/<application_name>.json

See also:

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