Is it possible to determine if Google Chrome is in incognito mode via a script?
Edit: I actually meant is it possible via user-script, but the answers assume JavaScript is running on a web page. I've re-asked the question here in regards to user scripts.
The functionality of this answer is Chrome version dependant. The most recent comment was this works in v90
Yes. The FileSystem API is disabled in incognito mode. Check out https://jsfiddle.net/w49x9f1a/ when you are and aren't in incognito mode.
Sample code:
var fs = window.RequestFileSystem || window.webkitRequestFileSystem;
if (!fs) {
console.log("check failed?");
} else {
fs(window.TEMPORARY,
100,
console.log.bind(console, "not in incognito mode"),
console.log.bind(console, "incognito mode"));
}console.log.bind statements (I used an anonymous function there to set a variable to true or false) –
Wetmore webkitRequestFileSystem in both contexts. –
Diphenyl navigator.serviceWorker is undefined in Firefox' incognito mode. Might be worth poking at Chrome's serviceWorker API to see if any differences pop up. –
Molloy disable-web-security flag and the FileSystem API will still work on it –
Damara 0. fs(window.TEMPORARY, 0, ... –
Eleen In Chrome 74 to 84.0.4147.135 you can determine this by estimating the available file system storage space
See the jsfiddle
if ('storage' in navigator && 'estimate' in navigator.storage) {
const {usage, quota} = await navigator.storage.estimate();
console.log(`Using ${usage} out of ${quota} bytes.`);
if(quota < 120000000){
console.log('Incognito')
} else {
console.log('Not Incognito')
}
} else {
console.log('Can not detect')
}
One way is to visit a unique URL and then check to see whether a link to that URL is treated as visited by CSS.
You can see an example of this in "Detecting Incognito" (Dead link).
Research paper by same author to replace Detecting Incognito link above
In main.html add an iframe,
<iframe id='testFrame' name='testFrame' onload='setUniqueSource(this)' src='' style="width:0; height:0; visibility:hidden;"></iframe>
, and some JavaScript code:
function checkResult() {
var a = frames[0].document.getElementById('test');
if (!a) return;
var color;
if (a.currentStyle) {
color = a.currentStyle.color;
} else {
color = frames[0].getComputedStyle(a, '').color;
}
var visited = (color == 'rgb(51, 102, 160)' || color == '#3366a0');
alert('mode is ' + (visited ? 'NOT Private' : 'Private'));
}
function setUniqueSource(frame) {
frame.src = "test.html?" + Math.random();
frame.onload = '';
}
Then in test.html that are loaded into the iFrame:
<style>
a:link { color: #336699; }
a:visited { color: #3366A0; }
</style>
<script>
setTimeout(function() {
var a = document.createElement('a');
a.href = location;
a.id = 'test';
document.body.appendChild(a);
parent.checkResult();
}, 100);
</script>
NOTE: trying this from the filesystem can make Chrome cry about "Unsafe Javascript". It will, however, work serving from a webserver.
:visited: hacks.mozilla.org/2010/03/… –
Comines You can, in JavaScript, see JHurrah's answer. Except for not highlighting links, all incognito mode does is not save browse history and cookies. From google help page:
- Webpages that you open and files downloaded while you are incognito aren't recorded in your browsing and download histories.
- All new cookies are deleted after you close all incognito windows that you've opened.
As you can see the differences between normal browsing and incognito happen after you visit the webpage, hence there is nothing that browser communicates to the server when it's in this mode.
You can see what exactly your browser sends to the server using one of many HTTP request analysers, like this one here. Compare the headers between normal session and incognito and you will see no difference.
For those looking for a solution, here's a brief rundown of the current methods of detecting Private Browsing modes in various browsers as of October 2021:
Chromium: Similar to Vinnie James's answer, call navigator.storage.estimate(), grab the quota property and compare it to performance.memory.jsHeapSizeLimit. If the quota property is less than jsHeapSizeLimit, it's incognito. If jsHeapSizeLimit is undefined, use 1073741824 (1 GiB).
Safari for macOS: Use safari.pushNotification.requestPermission on a non-existent push server & grab the error. If "gesture" does not appear in the error, it's in private mode.
Safari for iOS: Create an iframe & add an error event listener using contentWindow.applicationCache on the iframe. If the error trips, it's in private mode.
Firefox: navigator.serviceWorker will be undefined in a private window.
Internet Explorer: window.indexedDB will be undefined in InPrivate mode.
You can see an implementation of these methods in the detectIncognito script I have available on GitHub.
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 here.
If you are just working with a webpage, 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.
Update This seems to not be working anymore
This uses a promise to wait for the asynchronous code to set a flag, so we can use it synchronously afterward.
let isIncognito = await new Promise((resolve, reject)=>{
var fs = window.RequestFileSystem || window.webkitRequestFileSystem;
if (!fs) reject('Check incognito failed');
else fs(window.TEMPORARY, 100, ()=>resolve(false), ()=>resolve(true));
});
then we can do
if(isIncognito) alert('in incognito');
else alert('not in incognito');
Note, to use await you need to be inside an async function. If you're not, you can wrap all your code inside one to be able to
reject('Check incognito failed') with resolve(false) if I want isIncognito to be a boolean that is only ever true or false? Thanks. –
Siegel Syntax Error: await is a reserved word, and I think await always needs to be within an async function. So I think this code doesn't work. –
Siegel reject would raise an exception if it is called, and a value would not be returned, so isIncognito would always be true or false the way the code is written. However, you would also be able to use a 'resolve' there if you want a value returned. And it might depend on how the environment handles await in the global scope? It works on the chrome console in the global scope, but you could try wrapping everything in (async function() { 'everything here' })(); so it is run inside an async function –
Malachy isIncognito instead of the result, and run it afterwards in an async function: let isIncognito = new Promise( ...etc then somewhere else you'd have a function like (async function() { if( !(await isIncognito) ) {alert('not incognito') } })(); –
Malachy Other answers seem to be no longer valid in recent chrome versions.
The idea is to find out storage estimates to determine if the tab is incognito or not. Storage size is less for incognito tabs.
Run this code in both normal and incognito window and note down the quota size.
const {quota} = await navigator.storage.estimate();
console.log(quota);
use quota size difference to implement the logic for incognito mode detection.
below logic works for Chrome v105:
const { quota } = await navigator.storage.estimate();
if (quota.toString().length === 10) {
console.log("gotcha: this is incognito tab"); //quota = 1102885027
} else {
console.log("this is a normal tab"); //quota = 296630877388
}
Also, look at this solution for much wider support (includes other browsers as well) detectIncognito.ts
Version 106.0.5249.103 (Official Build) (x86_64), an incognito tab is showing "this is a normal tab". Detecting incognito mode via quota was fixed in 2020: bugs.chromium.org/p/chromium/issues/detail?id=1017120 –
Mound Quick function based on Alok's Answer (note: this is asynchronous)
Update - not working anymore
function ifIncognito(incog,func){
var fs = window.RequestFileSystem || window.webkitRequestFileSystem;
if (!fs) console.log("checking incognito failed");
else {
if(incog) fs(window.TEMPORARY, 100, ()=>{}, func);
else fs(window.TEMPORARY, 100, func, ()=>{});
}
}
usage:
ifIncognito(true, ()=>{ alert('in incognito') });
// or
ifIncognito(false, ()=>{ alert('not in incognito') });
Here is the suggested answer written in ES6 syntaxt and slightly cleand up.
const isIncognito = () => new Promise((resolve, reject) => {
const fs = window.RequestFileSystem || window.webkitRequestFileSystem;
if (!fs) {
reject('Cant determine whether browser is running in incognito mode!');
}
fs(window.TEMPORARY, 100, resolve.bind(null, false), resolve.bind(null, true));
});
// Usage
isIncognito()
.then(console.log)
.catch(console.error)
This works in May 2021: https://jsfiddle.net/2b1dk8oa/
The script has to be executed in a webpage, which is in an iframe.
try{
var ls = localStorage;
alert("You are not in Incognito Mode.");
}
catch(e) { alert("You are in Incognito Mode."); }
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