manifest.json

{
    "manifest_version": 2,

    "name": "Youtube Watchmarker",
    "description": "Automatically mark videos on Youtube that you have already watched.",
    "homepage_url": "https://sniklaus.com/",

    "version": "4.6.1",

    "permissions": ["alarms", "downloads", "history", "tabs", "cookies", "webRequest", "webRequestBlocking", "https://www.youtube.com/*"],

    "options_ui": {
        "page": "content/index.html",
        "open_in_tab": true
    },

    "icons": {
        "72": "content/icon.png"
    },

    "applications": {
        "gecko": {
            "id": "yourect@coderect.com",
            "strict_min_version": "55.0"
        }
    },

    "background": {
        "scripts": ["background.js"]
    },

    "content_scripts": [{
        "matches": ["*://www.youtube.com/*"],
        "css": [],
        "js": ["youtube.js"]
    }],

    "browser_action": {
        "browser_style": false,
        "default_title": "Youtube Watchmarker",
        "default_icon": {
            "72" : "content/icon.png"
        }
    }
}