It uses a cookie. You can't keep people from rejecting the cookie but most people don't.
Also,, it is only a one time fee of $29. You can spend at least $80 a month for Atlas Onepoint and it will do a bit more but you can get quite a bit of granularity with this program. It revolutionized my PPC campaign strategies.
[edit: Oh, by the way, prepare yourself for some substandard Ukranian-English documentation on the program but for $29 it really does a great job.]
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