I need to figure out a way uniquely identify each computer which visits the web site I am creating. Does anybody have any advice on how to achieve this?

Because i want the solution to work on all machines and all browsers (within reason) I am trying to create a solution using javascript.

I appreciate the help. Thanks.

EDIT:

Cookies will not do.

Some sites on the deep web uses the size of the window to track users. Maybe you can play with that kind of information and metadata, like user agent, IP, etc.
PHP sessions will be dropped when the user closes the browser, but depending on what you're doing can be useful.

@BrianValente aka the reason why you should never have your tor browser fullscreen when browsing deep web

Could you reconsider the requirement of unique identification?

@masterakay: are you by any chance employed by the NSA?

@kanduvisla hahahahaha nope

But yea I am open to any different or alternate ways of doing it. See the point was if I was making a native desktop application it would be easy to implement a one-machine-only mechanism. But since my client has asked for a browser based application.. I'm getting a headache
Is there a way to achieve it?

Oh and does anybody know how Facebook identifies devices? Like those trusted devices list?

@masterakay maybe you can utilize cache?

This should help you with JavaScript identification https://github.com/Valve/... it's a rather heavy solution compared to some other techniques but it has a high accuracy

@nofaceman hahaha you must the famous stack overflow

@nofaceman hey buddy. I've gone through Stack Overflow. I've googled a million articles. And I'm confused. I thought I could get help here you know?

@BoyBiscuit hey! I've already tried out fingerprintjs. And btw this is an old version, the new version collects a lot more parameters and generates a unique alpha numeric string for the machine.

My question now is: what if there are machines with the same configuration and hardware? Will not all the browsers have the same fingerprint then?

@masterakay what about cloned machines? I can try at school.

@BrianValente yes! Your school will have cloned machines. Unless someone has manually upgraded a browser or something, they should all be similar. Would you do me a favor and see it it shows different fingerprints? https://github.com/Valve/...

@masterakay I cloned those machines, some are untouched after cloning. I'll try tomorrow.

@BrianValente fine. Thanks! :)

@masterakay I tried on some cloned PCs, here are the results: http://wamod.ml/fingerprintjs2/...
Includes hashes and data on a JSON format.
The hashes are different, I don't know why. I don't have time to check the data, that's why I added the JSON too. It would be interesting if you tell me what's the difference there.

@BrianValente if they are cloned it should still be able to differentiate between computers but not all the time, it'll be less accurate though

@BrianValente Just got back from work. I'll look into the file once I am free. Thank you so much for trying it out!