Google Webmaster tool is very useful in SEO which is provided by Google for free. This tool helps us to communicate with google and adjust various aspects of how google sees our site like the list of External and internal links. It offers us to submit the sitemaps within our site. It tells the status of caching and indexing and adjust the crawl rate. We can see our websites health statistics.
Webmaster tool provides several of benefits like -
Access to search statistics on Google.
Latest data regarding incoming links and internal links.
Sends notification if your site has any crawl errors (misdirecting) and/or malware (spam, viruses, etc)
Show your keywords you are targeting and how effective they are.
Insights into crawling and indexing activity on the site.
Webmaster tool is my best for seo tool. This Research Tool will help you research appropriate words and phrases to include in your webpage's body text to aid in promotion. Google Analytics is another favorite SEO tool which is used to track the visitors to my site.