Is it possible to determine if Chrome is in incognito mode via a user-script?

I asked this question before but didn't make it clear that I meant in user script, not in JavaScript from a webpage.So I'll be more clear now.

Is it possible to determine if Google Chrome is in incognito m开发者_StackOverflow社区ode via a user-script (basically a script run as an extension in the browser, not a script being run on a webpage)?

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To detect whether a window is in incognito mode, check the incognito property of the relevant Tab or Window object. For example:

var bgPage = chrome.extension.getBackgroundPage();

function saveTabData(tab, data) {
  if (tab.incognito) {
    bgPage[tab.url] = data;       // Persist data ONLY in memory
  } else {
    localStorage[tab.url] = data; // OK to store data
}

http://code.google.com/chrome/extensions/overview.html

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If you are developing an Extension then you can use the tabs API to determine if a window/tab incognito.

More information can be found on code.google.com.

If you are just working with a webpage or a userscript, it is not easy, and it is designed to be that way. However, I have noticed that all attempts to open a database (window.database) fail when in incongnito, this is because when in incognito no trace of data is allowed to be left on the users machine.

I haven't tested it but I suspect all calls to localStorage fail too.

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Nowadays it's quite easy to do this from a content script. Just use

if(chrome.extension.inIncognitoContext) {
    //you're incognito
} else {
    //you're not
}