4 ms·

Why is it possible to detect whether you're using private mode or not? it's terrible, js shouldn't be aware of stuff like this.

lucideer 6y ago
There is no dedicated feature in js to detect private mode: private mode detection is done using a collection of innovative hacks and misuses of features. Tracking/detecting/fingerprinting/etc. is an arms race. Every feature a browser has (or could have and lacks), can be used as a variable to compile a tracking profile that identifies you and/or your general browser configuration (including but not limited to private mode). The biggest one of these though is something private mode can't control: IP. For that you need something like Tor or a VPN.
- tester34 6y ago
  IP may be very unreliable, so for some people it'd work pretty fine
- jakub_g 6y ago
  Like the parent said, typically it works like: - browser ships a feature X - they decide that X shouldn't be allowed in incognito (or that incognito mode returns fewer values, has lower quotas, uses different implementation that is slower/faster etc.) - inadvertently, this becomes incognito detection vector - people report the issue; the feature X is fixed - another thing is shipped which accidentally allows detecting incognito - ad infinitum
- account42 6y ago
  > Tracking/detecting/fingerprinting/etc. is an arms race. Every feature a browser has (or could have and lacks), can be used as a variable to compile a tracking profile that identifies you and/or your general browser configuration (including but not limited to private mode). Which is exactly why Firefox needs to push back on adding more and more of those features, especially those that are not needed for websites (rather than applications).
  - lucideer 6y ago
    I think you missed a part in my comment: > (or could have and lacks) Absence of features can also be used for detection. Any differentiator.

lucideer 6y ago

There is no dedicated feature in js to detect private mode: private mode detection is done using a collection of innovative hacks and misuses of features. Tracking/detecting/fingerprinting/etc. is an arms race. Every feature a browser has (or could have and lacks), can be used as a variable to compile a tracking profile that identifies you and/or your general browser configuration (including but not limited to private mode). The biggest one of these though is something private mode can't control: IP. For that you need something like Tor or a VPN.

tester34 6y ago
IP may be very unreliable, so for some people it'd work pretty fine
jakub_g 6y ago
Like the parent said, typically it works like: - browser ships a feature X - they decide that X shouldn't be allowed in incognito (or that incognito mode returns fewer values, has lower quotas, uses different implementation that is slower/faster etc.) - inadvertently, this becomes incognito detection vector - people report the issue; the feature X is fixed - another thing is shipped which accidentally allows detecting incognito - ad infinitum
account42 6y ago
> Tracking/detecting/fingerprinting/etc. is an arms race. Every feature a browser has (or could have and lacks), can be used as a variable to compile a tracking profile that identifies you and/or your general browser configuration (including but not limited to private mode). Which is exactly why Firefox needs to push back on adding more and more of those features, especially those that are not needed for websites (rather than applications).
- lucideer 6y ago
  I think you missed a part in my comment: > (or could have and lacks) Absence of features can also be used for detection. Any differentiator.