There is a useful browser extension called Keywords Everywhere. Discovered it recently. After you install the plugin whenever you google a word or phrase you will see the monthly search volume for that keyword or phrase displayed below the search bar and alongside the related search terms displayed at the bottom of the page below the search results.
The extension works with 8 sites to show search term volume and CPC costs. The free keyword research sites and keyword suggestion tools I like are
Use majestic.com to assess the link anchor terms used in competitor sites.
Go to keywordseverywhere.com to install the SEO extension into Chrome or Firefox. The full list of currently supported sites is shown on the homepage.
You will need an API key to use this free keyword browser extension. The API key is free. Here are the instructions for getting the Keywords Everywhere API key.
I like to protect my online anonymity and prefer not to be tracked around the Internet so I installed Keywords Everywhere into the browser I use least often. I am not suggesting the extension is used to track browsing habits but it could be a privacy risk and I like to take few chances in this regard. For me that least used browser is Chrome.
Keyword research tools will spark ideas for new posts so use them to get new content ideas as well as to improve on page SEO.