Prevent Tab Focus Detection

Prevent websites from detecting tab focus without breaking functionality

K instalaci tototo skriptu si budete muset nainstalovat rozšíření jako Tampermonkey, Greasemonkey nebo Violentmonkey.

You will need to install an extension such as Tampermonkey to install this script.

K instalaci tohoto skriptu si budete muset nainstalovat rozšíření jako Tampermonkey nebo Violentmonkey.

K instalaci tohoto skriptu si budete muset nainstalovat rozšíření jako Tampermonkey nebo Userscripts.

You will need to install an extension such as Tampermonkey to install this script.

K instalaci tohoto skriptu si budete muset nainstalovat manažer uživatelských skriptů.

(Už mám manažer uživatelských skriptů, nechte mě ho nainstalovat!)

You will need to install an extension such as Stylus to install this style.

You will need to install an extension such as Stylus to install this style.

You will need to install an extension such as Stylus to install this style.

You will need to install a user style manager extension to install this style.

You will need to install a user style manager extension to install this style.

You will need to install a user style manager extension to install this style.

(Už mám manažer uživatelských stylů, nechte mě ho nainstalovat!)

// ==UserScript==
// @name        Prevent Tab Focus Detection
// @description Prevent websites from detecting tab focus without breaking functionality
// @version     2026.02.12
// @author      Claude Sonnet 4.5
// @grant       none
// @inject-into auto
// @run-at      document-start
// @match       *://*/*
// @namespace https://greasyfork.org/users/1519047
// ==/UserScript==

(function() {
    'use strict';

    // Store original functions
    const originalGetters = {};
    const originalMethods = {};

    // Override document visibility properties
    const overrideProperty = (obj, prop, fakeValue) => {
        const descriptor = Object.getOwnPropertyDescriptor(obj, prop);
        if (descriptor && descriptor.get) {
            originalGetters[prop] = descriptor.get;
        }

        try {
            Object.defineProperty(obj, prop, {
                configurable: true,
                enumerable: true,
                get: function() {
                    return fakeValue;
                }
            });
        } catch(e) {
            console.debug('Tab focus prevention: Failed to override', prop, e);
        }
    };

    // Override all Page Visibility API properties (including vendor prefixes)
    overrideProperty(document, 'hidden', false);
    overrideProperty(document, 'visibilityState', 'visible');
    overrideProperty(document, 'webkitHidden', false);
    overrideProperty(document, 'webkitVisibilityState', 'visible');
    overrideProperty(document, 'mozHidden', false);
    overrideProperty(document, 'mozVisibilityState', 'visible');
    overrideProperty(document, 'msHidden', false);
    overrideProperty(document, 'msVisibilityState', 'visible');

    // Override hasFocus methods to always return true
    if (document.hasFocus) {
        originalMethods.documentHasFocus = document.hasFocus;
        document.hasFocus = function() {
            return true;
        };
    }

    if (window.hasFocus) {
        originalMethods.windowHasFocus = window.hasFocus;
        window.hasFocus = function() {
            return true;
        };
    }

    // Intercept visibility change events
    const interceptEvent = (e) => {
        e.stopImmediatePropagation();
    };

    // Only intercept Page Visibility API events (safest approach)
    const eventsToIntercept = [
        'visibilitychange',
        'webkitvisibilitychange',
        'mozvisibilitychange',
        'msvisibilitychange'
    ];

    eventsToIntercept.forEach(eventType => {
        window.addEventListener(eventType, interceptEvent, true);
        document.addEventListener(eventType, interceptEvent, true);
    });

    console.debug('Tab focus detection prevention active');
})();