There are many free SEO keyword research tools out there, but none of them are 100% accurate. This is why one must use multiple tools to obtain the most amount of keywords and improve the accuracy of the data. Below are some of the best ones that we put together.
1. Google Keyword Planner
This is one of the best free SEO keyword research tools used for paid search primarily and can help discover keywords and identify search volume changes for the past few months or years. One can also see the competition from other websites and the average CPC (cost per click) ad spending so SEO can help reduce the costs for the PPC targeted landing pages.
2. Ahrefs Keyword Generator
Another one of the best free SEO keyword research tools is Ahrefs Keyword Generator. It can let you discover not only keywords for Google, but also Bing YouTube, and Amazon. It will also tell you the difficulty of ranking the respective keywords based on competitor backlinks on the top search results. Alternatively, the paid version has a lot more capabilities such as CTR for both organic and paid search, global search volume by country, see parent topic or categories sorted out for you, see search result from competitive landscape, see Yahoo, Yandex, Baidu, Daum, Naver, and Seznam search engines.
Summary
Use Google Keyword Planner if you want to know competition level, and paid search data, and use Ahrefs Keyword Generator if you want to research keywords in other search engines.