One of the fundamentals of SEO rules is targeted keyword research. If you start with proper keywords, your website will start with an advantage for SEO and this will directly benefit your sales on your website. Though search engines prefer engaging and compelling website content, but they will not send you enough traffic if you do not include keywords related to your website in your content with a suitable keyword density. In view of this, you should always make use of best keyword research tool.
Another indirect benefit you get while doing keyword research is that you are able to gain deep insights into your market segment and trends which you can then benefit from while creating an overall content strategy for your website. And naturally you will now be asking which is the best keyword research tool?
If you would prefer a free option, then the best keyword research tool is undoubtedly Keyword Planner available in the Google Adwords. Its data comes from the dominant search engine and therefore is more reliable than most other keyword research tools. It gives you multiple options for doing your research and you can get local searches, global searches and advertiser competition for a keyword and additionally you also get the cost per click for these keywords which are an indicator of the potential profitability of the keyword. While it is free, you should keep in mind that the user interface and the kinds of filtering you can apply on the keywords produced by this best keyword research tool is quite limited.
Two other keyword research tools who produce a data scrapped from Google Suggest are Keywordtool.io and Ubersuggest. Both these give you keywords based on the suggestions Google gives while users are searching for a keyword. The main benefit is that these give long tail keywords and these keywords are actually what people are searching. However, both of these do not give the search volume for any of the Google suggest queries which is a kind of handicap.
The best keyword research tool in my opinion is LongTailPro because it takes data from the Google Keyword Tool but then allows you to apply multiple filters based on the length of keywords or minimum search volume etc which is a great help in deciding low competition long tail keywords. The pro version of LongTailPro also gives data about competition about a particular keyword and also available exact match domain names.