SEO course › Part 2: Keyword research
Paid keyword research tools such as Ahrefs and Semrush give you much larger keyword databases, keyword difficulty scores, competitor data and rank tracking in one place. They save time and reveal which keywords other sites rank for. They are useful once your site grows, but beginners can learn a great deal with free tools first.
This lesson explains what paid tools add, how Ahrefs and Semrush compare in general terms, and how to decide if you need one.
What do paid keyword research tools do that free tools do not?
Free tools like Google Keyword Planner and Google Trends are a strong start. Our lesson on free keyword research tools covers them.
Paid keyword research tools go further in a few ways:
- Bigger keyword databases: thousands of related ideas from a single seed keyword, with filters by word count, volume and difficulty.
- Keyword difficulty scores: an estimate of how hard it is to rank organically, which Keyword Planner does not provide.
- Competitor research: see the keywords another website ranks for and roughly how much traffic it gets.
- SERP overviews: see which pages rank for a keyword, with their estimated links and traffic.
- Rank tracking: monitor where your pages rank for chosen keywords over time.
- Intent labels and grouping: many tools tag keywords by likely intent and group similar terms.
Remember that the volumes and difficulty scores in these tools are estimates. Each tool uses its own data and formula. See our lesson on keyword metrics for how to read them.
What is Ahrefs used for in keyword research?
Ahrefs began as a backlink (link) analysis tool and grew into a full SEO suite. Its Keywords Explorer tool lets you enter seed keywords and see related terms, questions, estimated volume, keyword difficulty and the current top-ranking pages.
Ahrefs is known for its link data. Its keyword difficulty score leans heavily on how many links the top-ranking pages have. Its Site Explorer lets you enter a competitor’s domain and see the keywords that bring it organic traffic.
Ahrefs has also offered free tools for website owners, with limited features. Check its website for the current options.
What is Semrush used for in keyword research?
Semrush is an all-in-one marketing platform covering SEO, PPC (paid search), content and competitor research. For keywords, its Keyword Magic Tool expands a seed keyword into large lists grouped by subtopic, and Keyword Overview gives a quick summary of a single term.
Semrush also has a Keyword Gap tool to compare the keywords of several domains, plus position tracking and site audits. Because it covers paid search too, it suits teams that run both SEO and Google Ads. Learn more about paid search in our PPC section.
Like Ahrefs, Semrush has offered a free account with limited daily use. Features and limits change often, so check the current terms before signing up.
How do Ahrefs and Semrush compare?
Both tools are widely used and highly capable. The differences are more about focus and workflow than quality.
| Feature | Ahrefs | Semrush |
|---|---|---|
| Keyword ideas from a seed | Yes, via Keywords Explorer | Yes, via Keyword Magic Tool |
| Keyword difficulty score | Yes, own 0–100 scale | Yes, own 0–100 scale |
| Competitor keyword data | Yes, via Site Explorer | Yes, via domain and organic research |
| Keyword gap comparison | Yes | Yes |
| Paid search data | Limited | Broader PPC features |
| Best known for | Backlink data | All-in-one marketing suite |
Other paid options exist, such as Moz Pro and SE Ranking. Many offer free trials, so you can test before you commit.
When is it worth paying for a keyword tool?
A paid keyword tool makes sense when the time it saves or the insight it gives is worth more than its cost.
Signs you may need one
- You publish content regularly and need a steady flow of keyword ideas.
- You want to study what competitors rank for.
- You manage SEO for clients or several websites.
- You need to track rankings for many keywords.
Signs you can wait
- Your website is new and has only a few pages.
- You serve one local area with a small number of services.
- Free tools and Search Console already give you more ideas than you can write about.
For example, a dental clinic in Pune with ten service pages can do well with free tools. A digital agency in Hyderabad writing content for twenty clients will likely save many hours with a paid tool.
How do you get the most from a paid tool?
If you do pay, a clear routine prevents wasted time:
- Start with your seed keywords and set the right country, such as India.
- Filter out keywords with difficulty far above what your site can handle.
- Enter two or three competitors and export the keywords they rank for.
- Remove irrelevant terms and group the rest by topic.
- Check the actual Google results for your top choices before writing.
- Add your chosen keywords to rank tracking to measure progress.
Always sanity-check tool data against your own Google Search Console data, which shows real queries for your site.
Common mistakes to avoid
- Buying a paid tool before you understand the basics of keyword research.
- Treating estimated volume and traffic numbers as exact.
- Comparing keyword difficulty from Ahrefs with difficulty from Semrush; the scales differ.
- Exporting huge keyword lists and never turning them into pages.
Key takeaways
- Paid keyword research tools add large databases, difficulty scores, competitor data and rank tracking.
- Ahrefs is best known for link data; Semrush for its all-in-one marketing suite.
- All numbers in these tools are estimates and differ between tools.
- Free tools are enough for many small and local websites.
- Test with a trial before committing, and check current features and pricing yourself.
Frequently asked questions
Is Ahrefs or Semrush better for keyword research?
Neither is clearly better for everyone. Both are strong; try each with a trial and choose the one whose data and workflow suit you.
Do I need a paid keyword tool to rank on Google?
No. Google does not favor sites that use any particular tool. Many sites rank well using only free tools and good content.
Why do Ahrefs and Semrush show different search volumes?
Each tool estimates volume from its own data sources and models. Pick one tool and use it consistently to compare keywords.
Previous lesson: Free keyword research tools: Google Keyword Planner, Google Trends and more
Next lesson: Google Autocomplete for keyword research, plus People Also Ask and Related Searches