Not all websites implement our on-site analytics and publish the results. For these sites, we show estimated metrics based on traffic patterns across the web as a whole. We identify these patterns by looking at the activity of millions of web users throughout the world, and using data normalization to correct for any biases.

The more traffic a site gets, the more data we have to calculate estimated metrics. Estimates are more reliable the closer a site is to being ranked #1. Global traffic ranks of 100,000+ are subject to large fluctuations and should be considered rough estimates.

If a site has Certified Metrics instead of estimated, that means its owner has installed code allowing us to directly measure their traffic. These metrics have a greater level of accuracy, no matter what the ranking.

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