One of the first keyword research tools ever used is still provided by Google as part of their Adwords (now Google Ads) paid advertising services. Click here. It's free to use but you may have to give them a credit card to set up an account.

You can insert a seed keyword to get more ideas based around your original idea.

You also get an estimate of the total number of monthly searches for each keyword, based on Google's own data.

This Google keyword research tool is FREE.

Autocomplete is a feature within Google Search that makes it faster to complete searches that you start to type. Their automated systems generate predictions that help people save time by allowing them to quickly complete the search they already intended to do.

The suggestions they serve up are based on a vast amount of data that helps Google predict what a searcher will type next.

Autocomplete (AKA: 'word completion') was originally created to help people with disabilities enter queries with fewer keystrokes.

AlsoAsked uses Google’s People Also Ask queries to give you valuable insights into search intent. It is heavily focused on searcher intent that allows you to visually map the relationships between topics.

It offers 3 free searches but operates as a subscription service with plans starting at $15 a month.

Keywords Everywhere is a browser extension that pulls the "People Also Search For" and "Related" keywords from Google & Bing and shows them to you with the volume metrics right inside the search pages.

Keywords Everywhere also allows access to keyword metrics for any list of keywords and lets you download the list in Excel, CSV or PDF file formats.

No monthly subscriptions. Pay as you go.

1 credit for each keyword beginning with 100,000 keywords for $10.

Select where the resulting ideas come from – Google autocomplete, Reddit and Quora, Google’s People Also Ask, Keyword Discovery, or Content Explorer.

WordStream's Free Keyword Tool gives you lots of options.

You can find new keywords and prioritize them based on monthly volume.

Enter a keyword or website URL to get hundreds of relevant keyword results, tailored to your industry and location.

You can also enter a website URL – such as a competitor’s homepage – to get contextual keyword suggestions and ideas to help you compete against similar businesses.

The Free Keyword Tool is FREE. Click here.

This free long-tail keyword tool generates ideas, including search queries and underlying search intents.

From there, you identify possible clusters.

It allows you to input up to 10 topics or keywords, the preferred language and country.

Ahrefs (pronounced 'H-refs') has a great suite of paid tools. (See below)

They offer a number of free tools too. You might begin with Webmaster Tools.

They help you monitor your SEO health by scanning your website for 100+ common issues and giving advice on how to fix those issues.

Analyze your website's backlink profile.

See the keywords that are bring traffic to your website and compare your performance to your competitor's.

Scroll to the bottom of any Ahrefs page for a variety of free tools, checkers and keyword analyzers.

Moz Keyword Explorer is the venerable keyword research and analysis tool that is part of the Moz Pro SEO Toolset. (see below)

Analyze keywords by search volume.

Find keywords in question format.

Check keyword difficulty.

Perform competitor analysis.

Search keyword suggestions and ranking keywords by country for better international SEO strategies.

Souvle is a very basic free keyword research tool. It's best used for initial brainstorming ideas.

You type in a keyword and get results including estimated monthly queries, CPC and keyword difficulty.

You can select the search engines and other sites for specific terms related to those properties. 9 different properties, including Google, Bing, Amazon, Wikipedia, Answers, ebay and Overstock.

KeywordTool.io is another 'Autocomplete type tool for SEO. You only get 5 autocomplete suggestions for a search term in the free version.

Keyword Tool Pro will give up to 10 keywords for one search term on Google, YouTube, and Bing, 10 keywords on Amazon, 10 keywords on eBay, and 5 keywords on Google Play Store, making it one of the best free keyword research tools available. 

KeywordTool also executes the Alphabet Soup method of keyword research.

The free version of Keyword Tool can generate up to 750+ keywords from Google autocomplete in seconds.

The advanced version of Keyword Tool, Keyword Tool Pro, provides on average two times more keywords in comparison to the free version and offers a handful of other useful features.

AnswerThePublic listens in to autocomplete data from search engines like Google then quickly cranks out every useful phrase and question people are asking around that keyword.

It's especially good at finding 'question queries.'

They suggest using it when creating, not only content, but services.

AnswerThePublic was recently acquired by Neil Patel and Ubersuggest.

There are FREE and PAID options.

This free, bulk keyword research tool discovers user's needs and content opportunities at scale.

Think of it as an bulk Answer The Public / Ubersuggest alternative tool.

You can select 5 different countries.

Keyword Atlas is software you buy and download to your computer. It's one of the best keyword tools for SEO among the affordable options.

Keyword Atlas allows you to select 21 different sources, including Google, Bing, DuckDuckGo, YouTube, Amazon, eBay, Etsy, Target, Walmart and Wikipedia. Generate related keywords from 6 different sources.

Then export the results to a spreadsheet to filter and sort.

Track website positions and rankings for
any site (up to 20 total) with the Position Tracking Tool from SEMRUSH.

Use Position Tracking to monitor your keywords, search intent landing pages, domains for your site and competitors.

Identify which websites you are competing with on target keywords and see where you can beat your competition.

Get daily rankings for domains, subdomains, subfolders and URLs for up to 5,000 Keywords.

See your domain’s visibility, ranking trends, and estimated traffic. Leverage top-ranking keywords and boost low performers.

If you can afford it, subscribing to a suite of tools gives you a leg up on the competition.

SEMRUSH allows you to do SEO, content marketing, competitive analysis, social media and PPC research.

You can find national and local keywords, analyze any domain's backlink profile and run technical SEO audits.

Track SERP positions daily.

A free 7-day trial is available. Monthly subscriptions start at $119 for 5 projects.

Ahrefs core tools include Site Explorer, Keywords Explorer, Site Audit, Rank Tracker and Content Explorer.

These tools allow you to audit and optimize your website, analyze your competitors, find profitable keywords, discover the top performing content in your industry or niche and track your ranking.

Truly, an All-In-One SEO Toolset.

Moz has been a respected SEO toolset provider, offering keyword research, link research, rank tracking and technical SEO audits.

Check them out here.

Take advantage of their 30-day free trial. Subscriptions begin at $99/mo. They also have a Local package for brick and mortar businesses.

Ubersuggest is a respected tool for SEO and all various components. It allows keyword research, competitive analysis, link-building and rank tracking.

Ubersuggest allows you to get insight into the strategies that are working for others in your market so you can adopt them, improve them, and gain an edge.

It reports issues that could be hurting your search engine optimization from missing sitemaps or robots files to pages that are blocked from appearing is search engines.

Limited monthly subscriptions start at $29 for entrepreneurs and small businesses operating 1 website. 

Billed as more than just a keyword research tool, KeySearch includes competitive research, backlink checker and rank tracking.

The free trial gives you 5 free daily searches. The starter package give you 200 daily searches and includes rank tracking. The Pro version increases daily searches to 500 and rank tracking of 200 terms for $34.