Choosing the right keyword is the foundation of successful search engine optimization. Fortunately there are a number of free online tools to help you identify potential keywords and analyze their strengths.

Here is a list of tools for researching keywords. There are tools to generate keyword ideas. There are also tools to rank keywords, track searches, compare multiple terms, and more. All of these tools are free,

For more on keyword research, read our recent three-part series, “Optimizing a Page for Search Engines."

Keyword Research Tools

Google AdWords Keyword Tool. This is Google’s official AdWords keyword research tool. The tool generates keyword ideas and analytical information on each term.

SEO Book Keyword Suggestion Tool. SEO Book’s Keyword Suggestion tool is powered by Wordtracker and cross references Google, Yahoo!, Bing, and more. It is free upon joining SEO Book for a free membership.

Google Insights for Search. Compare search volume patterns across specific regions, categories, time frames and properties. Narrow data to specific categories, anticipate seasonality, analyze geographic distribution, and search patterns in other Google properties.

Google Trends. Use commas to compare multiple search terms. Enter up to five topics and see how often they’ve been searched on Google over time.

Microsoft Advertising Intelligence. Microsoft Advertising Intelligence is a keyword research and optimization tool that operates in Microsoft Office Excel. It provides keyword expansion, research, pricing and KPI — key performance indicator — data. Build out lists of suggested keywords and develop keyword strategies based on Bing and Yahoo! network data.

Free Search Term Suggestion Tool. This tool by Keyword Discovery accesses data compiled from over 200 search engines worldwide. Type a seed keyword and generate the top 100 keywords.

SEMRush. Access data from more than 80 million keywords. For any site, get Google keywords, find hidden keywords, investigate long-tail keywords, discover competitors’ sites with common Google keywords, and more. A free user has a limit of only 10 queries/day and 10 results/query.

KGen. KGen (Keyword Generator) is an add-on for Firefox. KGen retrieves every word of a page and lists how many times they appear, their weight, and their average position in the page.