How to Get Extension Manifest Information

By David Walsh on July 10, 2022

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:

chrome.runtime.getManifest()

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

{
    "author": "https://metamask.io",
    "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": [
                "disable-console.js",
                "globalthis.js",
                "lockdown-install.js",
                "lockdown-run.js",
                "lockdown-more.js",
                "contentscript.js"
            ],
            "matches": [
                "file://*/*",
                "http://*/*",
                "https://*/*"
            ],
            "run_at": "document_start"
        }
    ],
    "current_locale": "en_US",
    "default_locale": "en",
    "description": "An Ethereum Wallet in your Browser",
    "externally_connectable": {
        "ids": [
            "*"
        ],
        "matches": [
            "https://metamask.io/*"
        ]
    },
    "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": [
        "storage",
        "unlimitedStorage",
        "clipboardWrite",
        "http://localhost:8545/",
        "https://*.infura.io/",
        "https://lattice.gridplus.io/*",
        "activeTab",
        "webRequest",
        "*://*.eth/",
        "notifications"
    ],
    "short_name": "MetaMask",
    "update_url": "https://clients2.google.com/service/update2/crx",
    "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!

Recent Features

By Chris CoyierAugust 13, 2013

Chris Coyier’s Favorite CodePen Demos

David asked me if I'd be up for a guest post picking out some of my favorite Pens from CodePen. A daunting task! There are so many! I managed to pick a few though that have blown me away over the past few months. If you...

By David WalshNovember 2, 2015

JavaScript Promise API

While synchronous code is easier to follow and debug, async is generally better for performance and flexibility. Why "hold up the show" when you can trigger numerous requests at once and then handle them when each is ready? Promises are becoming a big part of the JavaScript world...

Incredible Demos

By David WalshJune 22, 2009

MooTools Fun with Fx.Shake

Adding movement to your website is a great way to attract attention to specific elements that you want users to notice. Of course you could use Flash or an animated GIF to achieve the movement effect but graphics can be difficult to maintain. Enter...

By David WalshApril 8, 2010

Create a Trailing Mouse Cursor Effect Using MooTools

Remember the old days of DHTML and effects that were an achievement to create but had absolutely no value? Well, a trailing mouse cursor script is sorta like that. And I'm sorta the type of guy that creates effects just because I can.