Just looked at similar web and tested 3 sites I work with. They are pretty accurate on their traffic estimates. Anyone know how that is calculated?

Estimated using samples gathered with analytics through third-party browser plugins.

http://support.similarweb.com/customer/en/portal/articles/13...

I think they use DNS data to estimate the amount of traffic.

I'm the founder of Datanyze.

We raised $2M in funding so far, but we are bigger than BW (and I'm sure SimilarTech) in terms of revenue.