Stealth Mode (Tracking protection)
Many websites gather information about their visitors, such as their IP address, installed browser and operating system, screen resolution, and even the page from which a visitor was redirected. Some web pages use cookies to mark your browser and save your personal settings and preferences, or to "recognize" you upon your next visit. Stealth Mode (or Tracking protection in AdGuard for Windows and AdGuard Browser Extension) safeguards your personal information from such data- and statistics-gathering systems.
You can flexibly adjust the work of Stealth Mode: for instance, you can prohibit the website from receiving the search request you used to find it on the Internet, automatically delete both third-party and the website's own cookies, turn off browser geolocation sharing that can be used to track your whereabouts, and hide your true IP address or even replace it with an arbitrary one.
Below we will list and describe the main features and options that you can control in the Stealth Mode settings. They are split into four groups: General, Tracking methods, Browser API, and Miscellaneous.
Some options may not be available depending on the particular product due to OS or other limitations.
General
Hide search queries
When you get directed to a website from Google, Yahoo, or any other search engine, this option hides the search query that you used to find that website.
Send signals to opt out of tracking
Sends the Global Privacy Control and Do Not Track signals to the websites you visit.
Remove tracking parameters from URLs
If you enable this option, AdGuard will strip tracking parameters like utm_* and fb_ref from pages’ URLs.
Tracking methods
Delete third-party cookies
Websites use cookies to store your information and preferences, such as the language you selected, your location, or the list of items in your shopping cart. When you return to a website, your browser sends back the cookies belonging to that website, which allows it to "remember" your data.
Third-party cookies are those implemented by a website that is different from the one you are currently browsing. For example, cnn.com may have a Facebook "Like" widget on its homepage. This widget will implement a cookie that may be read later by Facebook. Some advertisers use such cookies to track what other sites you visit where their ads are placed.
Set a time period (in minutes) at the end of which all third-party cookies will be destroyed. Set the timer to 0 to block them completely.
This setting deletes all third-party cookies, including the information of your logins through social networks or other third-party services. You may have to periodically re-log in to some websites and face other cookie-related issues. To block only tracking cookies, use AdGuard Tracking Protection filter.
Delete first-party cookies (not recommended)
Set a time period (in minutes) at the end of which all cookies will be destroyed. Set the timer to 0 to block them completely.
We do not recommend enabling this option as it may severely interfere with the work of certain websites.
Block ETag and If-None-Match headers
When a browser addresses a page, the server assigns an ETag to that page. This ETag is used by the browser to cache the page's contents. Upon subsequent requests, the browser sends the ETag to the corresponding server, thus letting the server learn the visitor’s identity. As long as the site's files are cached, the ETag is sent every time your browser addresses this site. If the site has embedded content from another server (such as an image or iframe), that server can track your activities without your knowledge.
Block third-party Authorization header
"Authorization" header value is cached by the browser, and then is sent alongside every request to that domain. It means that it can be used for tracking purposes just like cookies.
Browser API
Block WebRTC
WebRTC (Web Real-Time Communication) is a technology that allows direct streaming of data between browsers and apps. It can let others know your true IP address, even if you use a proxy or VPN. Enabling this option can disrupt the work of certain browser applications, such as messengers, chats, cinemas, or games.
Block Push API
The Push API enables servers to send messages to web applications regardless of the activity status of your browser. Thus, you may see notifications from various websites even if your browser is hidden in the tray or not launched. Enable this option to block the browser's Push API completely.
Block Location API
Enabling this option will prevent the browser from sending GPS data that could be used to determine your location, modify your search results, or otherwise influence your web experience.
Block Flash
The Flash Player plugin has become increasingly vulnerable to such online threats as viruses and hackers; it may also significantly increase website load times. Turning this setting on makes AdGuard block browsers' ability to detect components (such as plugins and ActiveXObject objects) that allow Flash to display content. This effectively means that browsers are unable to support Flash.
Block Java
Some websites and web services still use the old technology to support Java plugins. The Java plugin API, which is the basis of Java plugins, has serious security flaws. For security purposes, you can disable such plugins. Nevertheless, even if you decide to use the "Block Java" option, JavaScript will still be enabled.
Miscellaneous
Hide Referer from third parties
Referer is an HTTP header used in browser-to-server requests. It contains the URL of the request source. When you navigate from one page to another, Referer saves the URL of the initial page. The server that hosts the destination web page often has software that parses Referer and extracts various pieces of information from it. Enabling the Hide Referer from third-parties option hides the current website from third-party sites by altering the HTTP header.
You can also set an arbitrary value for Referer by entering it into the Custom Referer field. To use default Referer, leave the field blank.
Note that to be able to filter traffic, AdGuard applications 'intercept' browser-to-server requests. Requests to ad, tracking, and phishing servers may be altered before sending them to the server or blocked completely. Same goes for the Hide Referer from third parties option: AdGuard intercepts HTTP(S) requests, in particular to remove or change the Referer header if this option is enabled. However, it happens only after these requests “leave” the browser. This means that if you monitor Referer inside the browser (for example, with the help of Chrome's Developer Tools), you will see the original Referer because the request hasn't reached AdGuard yet. You can use software like Fiddler to make sure that Referer gets altered correctly.
On the other hand, due to the nature of all browser extensions, AdGuard Browser Extension works 'inside' the browser. It will alter the Referer right then and there, so Developer Tools will show the desired Referer for your requests.
Hide User-Agent
When you visit a website, your browser sends its information to the server. It looks like a text line that is part of an HTTP request that begins with "User-Agent:". It usually includes the name and version of the browser, the operating system, and language settings. We cut User-Agent from identifying information so that advertisers cannot obtain it.
You can also set an arbitrary value for User-Agent by entering it into the Custom User-Agent field. To use default User-Agent, leave the field blank.
Mask IP address
Stealth Mode cannot hide your IP address. However, we can conceal it so that websites you visit will think you are a proxy. Sometimes this helps, and websites ignore your true IP address.
You can set an arbitrary IP address, which you would like others to perceive as yours, by simply entering it into the corresponding field. To use the default IP address, leave the field blank.
Remove X-Client-Data header
It forbids Google Chrome from sending its version and modification information with requests to Google domains (including Double Click and Google Analytics).
Protect against DPI
The Deep Packet Inspection is a system of deep analysis and filtering of traffic by packet content, as well as the accumulation of statistical data. Using this technology, ISPs have the ability to control the passing traffic and limit access to content for their clients.
AdGuard can modify outgoing packet data so that the client does not fall under the DPI blocking criteria. This means that by enabling this option, users can get access to the content they want. Not all DPI systems can be bypassed at this time, but we are constantly working to improve this.
The "Protect from DPI" feature is already implemented in AdGuard for Windows, AdGuard for Mac, and AdGuard for Android.
If this feature is enabled in AdGuard for Windows, it may interfere with ESET antivirus. Anti-DPI will prevent ESET from filtering traffic, leaving blacklisted and malicious websites unblocked.