Soolve, a centralized keyword research tool, also acts as a keyword aggregator in that it gives you keyword suggestions from various search engine platforms at one time.
Google Trends is one keyword research tool that gives you valuable insights into keyword trends over a period of time. The results are presented as graphs to give you an idea of the relative popularity of a keyword at a specific time throughout the year.
Question DB is another keyword research tool that gives you relevant insights into customers ‘most asked questions. It lets you peek into users’ minds and see which questions they have asked most over the years.
Keyword Surfer is a keyword research tool that suggests similar keywords to the one you enter but also gives you volume-based data about a specific keyword.
Google Search Console helps you track your website’s performance and organic reach. It provides insights on URLs, crawls, indexes, number of clicks, impressions, and the position of your website on Google.
Bulk Keyword Generator is another one of those free keyword research tools that are simple to use. The research tool suggests relevant and local keywords according to your company or business's industry.
Ahrefs Keyword Explorer has become one of the best and most comprehensive keyword research tools available. It has a huge keyword database (of over 7 million keywords) that is continuously growing.