Google webmaster tools, Google Analytics, Open site explorer, Alexa, Website grader are some of the free and basic tools which are commonly used for SEO. However, there are also many paid tools like Seo Moz, spydermate, bulkdachecker, readily available in the market.
Google webmaster tools: It is one of the most useful SEO tools. It is designed for the webmasters. It helps webmasters communicate with Google and evaluate and maintain their website’s performance in search engine results. Using webmaster, one can identify the issues related to a website such as crawling errors, malware issues, etc. It is a free service offered by Google, anyone who has a site can use it.
Google analytics: It is a free Web analytics service offered by Google. It is designed to provide analytical and statistical tools for SEO and digital marketing. It enables you to analyze website traffic and other activities that take place on your website. Anyone who has a Google account can use this service.
Open site explorer: It is a Mozscape index-powered workhorse which is designed to research backlinks, find link-building opportunities and find out links that may impact rank badly.
Alexa: It is a global ranking system that compiles a list of most popular websites based on the web traffic data and accordingly provides Alexa Rank to a website. The lower the Alexa rank, the more popular a website, e.g., a site with rank 150 will have more visitors than a site with rank 160.
Website grader: It is a free online tool designed to grade a website against some critical metrics like performance, SEO, security and mobile readiness.
Some Paid SEO Tools:
SEOMoz: It is a premium SEO web application designed for SEO. It provides analytics and insights to improve your search engine rankings. It is a collection of various SEO tools that cover all vital areas of SEO.
Spyder Mate: This software allows you to improve the ranking of your website as well as offers various methods to promote a website. It enables you to manage your web portal to attract more and more traffic to your site.
Bulkdachecker: It is used to check the Domain Authority of Multiple Websites simultaneously.