Alexa Rank is the most commonly used metrics when it comes to website ranking globally and by country. Alexa rank is based upon the total number of users a website gets regardless of the traffic sources (organic, social, referral or direct). Website that gets most traffic is ranked #1. Alexa uses a secret ranking algorithm which is updated daily, the estimated rank becomes more accurate as the website grows and gets more visitors. Top 500 websites are therefore get more accurate ranking data describing traffic, demographics and competitors.
Semrush Rank unlike moz rank focuses mainly on organic traffic and paid traffic; dealing with both Search Engine Optimization(SEO) and Search Engine Marketing (SEM) respectively. A website/domain which has most keywords in the top 100 results (starting from top 10 progressively) is ranked as the best website. For example , Youtube is ranked at number 2 with 109 million keywords. Semrush uses different google's geo databases to obtain it's ranking. By default US database depicts website semrush Rank.
Moz Rank essentially ranks websites based on the volume of backlinks the domain has. Websites with more links to it is said to be authoritative. Thus the term Domain Authority and Page Authority, check our Authority Checker for details.
Similarweb works the same as alexa rank in addition to ranking of android and Ios Apps. Similarweb widgets are used by webmaster to show a preview of website rank and number of visits. Unlike Alexa ,in similarweb domain data is updated on a monthly basis.
Quantcast exclusively measures websites which have implemented the asynchronous quantcast tag. Larger sites may also been measured through estimates. Among the key information provided include monthly traffic, rank of site by country and globally, with filtering based on mobile and desktop traffic.