How to Get Extension Manifest Information


Working on a web extension can be kinda wild — on one side you’re essentially just coding a website, on the other side you’re limited to what the browser says you can do in the extension execution environment. One change in that environment is coming January 2023 — pushing extensions to move to manifest version 3. I recently got curious about whether other popular extensions had completed the version 3 update.

Executing the following command in the background page (manifest version 2) or service worker (version 3) will provide you the extension’s manifest:


The getManifest call returns a large object detailing the extension’s manifest. Here’s what you’d see for the MetaMask browser extension:

    "author": "",
    "background": {
        "page": "background.html",
        "persistent": true
    "browser_action": {
        "default_icon": {
            "16": "images/icon-16.png",
            "19": "images/icon-19.png",
            "32": "images/icon-32.png",
            "38": "images/icon-38.png",
            "64": "images/icon-64.png",
        "default_popup": "popup.html",
        "default_title": "MetaMask"
    "commands": {
        "_execute_browser_action": {
            "suggested_key": {
                "chromeos": "Alt+Shift+M",
                "linux": "Alt+Shift+M",
                "mac": "Alt+Shift+M",
                "windows": "Alt+Shift+M"
    "content_scripts": [
            "all_frames": true,
            "js": [
            "matches": [
            "run_at": "document_start"
    "current_locale": "en_US",
    "default_locale": "en",
    "description": "An Ethereum Wallet in your Browser",
    "externally_connectable": {
        "ids": [
        "matches": [
    "icons": {
        "16": "images/icon-16.png",
        "19": "images/icon-19.png",
        "32": "images/icon-32.png",
        "38": "images/icon-38.png",
        "48": "images/icon-48.png",
        "64": "images/icon-64.png",
    "manifest_version": 2,
    "minimum_chrome_version": "66",
    "name": "MetaMask",
    "permissions": [
    "short_name": "MetaMask",
    "update_url": "",
    "version": "10.16.1"

Many of web extensions are still using manifest version 2, so many extension developers are pushing to finish manifest version 3 work!

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