The three SEO keyword research tools most people rely on are Google Keyword Planner (free), Semrush (paid) and Ahrefs (paid). Keyword Planner is the best place to start if you’re on a budget. Semrush is a strong all-in-one choice for agencies and growing businesses. Ahrefs is a favorite for competitor research and backlink data.
None of them is perfect, and all of their numbers are estimates. The right pick depends on your budget, your experience and what you need beyond keywords.
Here’s how each one works, where it falls short, and how to use them together.
Quick pick
- Just starting or on a tight budget: Google Keyword Planner, plus Google Search Console
- Agency or growing business that needs one tool for everything: Semrush
- Competitor research, content gaps and backlinks: Ahrefs
What a good keyword research tool should help you do
- Find ideas your audience actually searches for
- Compare demand between keywords
- Judge difficulty, meaning how hard it is to reach page one
- Understand intent: is the searcher learning, comparing or buying?
- Spot gaps: topics competitors rank for that you don’t
- Track trends and seasonality
Keep these in mind as you compare the three tools below.
1. Google Keyword Planner (free)
Keyword Planner lives inside Google Ads. It was built for advertisers, but it’s still one of the most useful free tools for SEO because the data comes from Google.
What it does well
- Keyword ideas from a seed term or a competitor’s URL
- Estimated monthly searches, trend charts, and 3-month and year-over-year changes
- Location and language targeting, which is great for local SEO
- Top-of-page bid ranges, a helpful signal of buying intent
Where it falls short
- Search volumes are usually shown as ranges (like 1K–10K) unless you run ads
- The Competition column shows advertiser competition, not SEO difficulty
- No competitor ranking data, backlink data or SERP analysis
Best for
Beginners, small businesses and anyone who wants free demand data straight from Google.
Want the full walkthrough? Read our step-by-step guide to Google Keyword Planner for SEO.
2. Semrush (paid)
Semrush is an all-in-one marketing platform. Keyword research is just one part. It also covers site audits, rank tracking, competitor research, backlinks and local SEO.
What it does well
- Keyword Magic Tool: huge lists of related keywords with filters for questions, intent and word count
- Keyword Overview: estimated volume, keyword difficulty, CPC, intent and SERP features in one view
- Competitor research: see which keywords a competitor’s site ranks for
- Keyword Gap: compare your site with competitors to find missing topics
- Position tracking: monitor your rankings over time
Where it falls short
- Paid plans are a real cost for freelancers and small businesses
- So many features that it can feel overwhelming at first
- The free account is very limited
Best for
Agencies managing multiple clients, in-house marketing teams, and businesses that want keywords, audits and tracking in one place.
3. Ahrefs (paid)
Ahrefs started as a backlink tool and grew into a full SEO suite. Many SEOs like it for clean data views and competitor research.
What it does well
- Keywords Explorer: estimated volume, keyword difficulty, estimated clicks and parent topics
- SERP overview: see the pages ranking for a keyword and their metrics
- Content Gap: find keywords competitors rank for and you don’t
- Site Explorer: one of the strongest backlink and competitor analysis tools
- Multiple search engines: keyword data beyond Google, such as YouTube and Amazon
Where it falls short
- Paid plans, with no traditional free trial
- Lower-tier plans have usage limits that can feel tight
- A learning curve for complete beginners
Best for
SEO specialists, content strategists, and businesses that care about competitor and backlink analysis as much as keywords.
Comparison table
| Feature | Google Keyword Planner | Semrush | Ahrefs |
|---|---|---|---|
| Cost | Free (Google Ads account) | Paid plans | Paid plans |
| Keyword ideas | Good | Extensive | Extensive |
| Search volume | Ranges or rounded estimates | Estimates | Estimates |
| SEO keyword difficulty | None (ad competition only) | Yes | Yes |
| Competitor keywords | No | Yes | Yes |
| Backlink analysis | No | Yes | Yes (a key strength) |
| Rank tracking | No | Yes | Yes |
| Best for | Beginners, tight budgets | Agencies, all-in-one | Competitor and backlink research |
Note on pricing: Semrush and Ahrefs change their plans and limits often. Check their pricing pages for current costs before you buy.
Don’t skip these free tools
Before paying for anything, use:
- Google Search Console: shows the real queries your site already appears for. Pages ranking in positions 8–20 are often your fastest wins
- Google Trends: compares interest over time and by region
- Google autocomplete and People Also Ask: real questions people type
- Free versions: Semrush and Ahrefs both offer limited free keyword tools or free accounts. Handy for occasional checks
For more options, see our list of free SEO tools.
How to use these tools together
A simple workflow that works for most sites:
- Search Console: find what you already rank for and which pages to improve
- Keyword Planner: expand ideas, check rough demand and seasonality, and set your location
- Semrush or Ahrefs: check difficulty, see what competitors rank for, and find gaps
- Google itself: look at page one to confirm intent and the content format
- Plan: group keywords into topics and give each main keyword one page
To structure that plan, read about content clusters and pillar pages and how many SEO keywords per page you should target.
Keyword tools and AI search
People now ask ChatGPT, Perplexity and Google’s AI Overviews long, conversational questions. Keyword tools don’t capture most of these, but they still show the core topics and questions behind them.
Both Semrush and Ahrefs have added features that track brand mentions in AI answers. They’re worth exploring if AI visibility matters to you, but the basics haven’t changed: answer real questions clearly, show real experience, and cover a topic completely.
Learn more about how answer engine optimization works and getting cited by AI answer engines.
Tips for better keyword research (whatever tool you use)
- Go after long-tail keywords. They’re more specific, usually easier to rank for, and often convert better. See long-tail keywords for local businesses
- Balance volume and difficulty. A new site should target realistic terms first. Here’s how to find high-traffic, low-competition keywords
- Match search intent. The page-one results show what Google thinks searchers want
- Avoid targeting one keyword on several pages, or they’ll compete. Read about keyword cannibalization
- Study competitors. A quick SEO competitor analysis shows what’s working in your niche
- Revisit your list every few months, because search behavior changes
Special cases:
- Video: how to add keywords to YouTube videos
- Marketplaces: Amazon search terms
- Online stores: our ecommerce SEO guide
- Multiple countries: international keyword and market research
Frequently asked questions
What is the best free keyword research tool?
Google Keyword Planner and Google Search Console together. Keyword Planner gives you ideas and demand. Search Console shows the queries you already rank for.
Is Semrush better than Ahrefs?
Neither is better for everyone. Semrush is often preferred as an all-in-one marketing platform. Ahrefs is often preferred for backlink and competitor research. Try both free versions and pick the one whose workflow you like.
Are search volumes in these tools accurate?
They’re estimates. Each tool uses its own data and models, so numbers often differ. Use them to compare keywords, not to predict exact traffic.
Does Keyword Planner show keyword difficulty?
No. Its Competition column shows advertiser competition. For SEO difficulty, use Semrush, Ahrefs, or check page one yourself.
Do I need a paid tool to do SEO?
Not to start. Many small sites grow with free tools. Paid tools save time and add competitor and backlink data as you scale.
How many tools should I use?
Usually one free combination (Search Console and Keyword Planner) plus one paid tool is plenty. More tools often means more conflicting numbers, not better decisions.
Final thoughts
The best SEO keyword research tool is the one you’ll actually use well. Start free with Google Keyword Planner and Search Console. When you need difficulty scores, competitor data and backlinks, add Semrush or Ahrefs.
Whatever you choose, the tool only finds the opportunity. Ranking still comes from matching intent, writing genuinely helpful content and building a well-linked site.
Next steps: work through our on-page SEO checklist, follow the guide to SEO for a new website, learn how to create SEO reports for clients, and keep up with the latest SEO trends for 2026.
About the author
Saurabh K. has been working in SEO and digital marketing for 10+ years, helping businesses grow their search traffic.
