6 Best Keyword Research Tools for SEO

Are you overwhelmed by the number of keyword research tools available? I’m not surprised. There are a lot of them around! Tools for SEO

But which, if any, is best?

To answer that question, I tested them all and marked them according to five essential criteria. (Keep reading to see what those criteria were.)

Here are the best keyword research tools for 2018 (as per our testing):

  1. Ahrefs Keywords Explorer (23/25 points)
  2. KWFinder (20/25 points)
  3. Moz Keyword Explorer (14/25 points)
  4. SEMRush Keyword Magic Tool (13/25 points)
  5. Long Tail Pro (12/25 points)
  6. SERPStat Keyword Research Tool (10/25 points)

Let’s take a deeper look at the testing criteria and results.

Beginner’s guide to keyword research

New to keyword research? Check out our

Beginner’s guide to keyword research

My criteria, methodology & results

In my everyday work (at Authority Hacker), I do a lot of keyword research.

Based on my experience, I believe that the perfect keyword research tool relies on five main criteria, which are:

  1. Keyword suggestions: It must find/suggest as many relevant keywords as possible.
  2. Data filtering: It must be able to trim down large keyword lists easily.
  3. Search volume trend: It must show a search trend for a keyword.
  4. Keyword difficulty: It must have a reliable keyword difficulty score.
  5. SERP analysis: It must have SERP analysis functionality.

My methodology, therefore, was simple:

I would test 6 big keyword research tools for all of these criteria, then assign a grade between 1-5 for each. This would result in an overall score out of twenty-five for each tool.


 For the “keyword suggestions” criteria, I used the same keyword—”massage”—in each keyword tool to make sure that the results were comparable.

Here are the detailed results:

Let’s take a look at a more detailed breakdown of each tool.

1. Ahrefs Keywords Explorer (23/25 points)

Number of keyword suggestions*: 5/5

Suggested: 892,576 keywords

Ahrefs pulled the maximum number of keyword suggestions and left all other tools far behind. Ahrefs’ Keyword Generator is powered by clickstream data and updates its database with fresh keywords every month.

Data filtering*: 4/5

Ahrefs allows you to filter the whole list of keyword suggestions by search volume and keyword difficulty. These two metrics are cached and always available for the entire database of keywords.

This tool has also got some unique keyword metrics (and thus filters) for the list of keyword suggestions not found in other tools such as:

  • Clicks
  • Clicks Per Search
  • Return Rate

But they will only be pulled after you click “Get metrics” button.

Search volume trend*: 4/5

Not only this tool shows the search volume trend starting from September 2015, but it also breaks it down further based on whether the searches result in actual clicks.

Search volume trend graphs is a visualization and does not show the search volume numbers for the past months.

Keyword difficulty*: 5/5

Keyword difficulty calculation in Ahrefs Keywords Explorer is entirely based on the backlink profiles of the top10 pages in SERP and nothing else. Yet we’ve found that Ahrefs offers the most reliable metric over any other tool.

SERP analysis*: 5/5

A very detailed SERP analysis. Ahrefs will show you the accurate backlinks numbers for the search results. You can also see the SERP features (if any). And it’s the only tool that shows how much search traffic the top ranking pages are getting (from all the keywords they rank for, not just from your target keyword).

2. KWFinder (20/25 points)


Number of keyword suggestions*: 2/5

Suggested: 954 keywords

The tool has three types of keyword ideas: suggestions, autocomplete, and questions, so I summed them up (after filtering out the duplicates).


 KWFinder caps keyword suggestions at 200 or 700, depending on your plan.

Data filtering*: 4/5

Filtering with KWFinder is a breeze. There’s just one drawback: keyword difficulty data isn’t instantly available for every keyword unless it’s been requested by any user previously (unlike Keywords Explorer from Ahrefs which shows keyword difficulty for all the keyword suggestions).

Search volume trend*: 5/5

The search volume trend is nicely laid out in organic KWFinder style with all the data you’d expect.

Keyword difficulty*: 5/5

They calculate it based on SEO stats (DA, PA, MR, MT pulled from MOZ) of the pages on the first page of Google.

In my work, I found KWFinder’s SEO difficulty metric to be surprisingly accurate. Plus, it is easy on the eyes.

SERP analysis*: 4/5

KWFinder’s SERP analysis is super simple and easy to digest. However, they’re using backlink data from MOZ, which is not a perfect source. Maybe they should think about switching to Majestic API.

3. Moz Keyword Explorer (14/25 points)

Moz keyword explorer overview

Number of keyword suggestions*: 2/5

Suggested: 1,000 keywords


 Moz has a limit of 1,000 keyword suggestions for any seed keyword.

Data filtering*: 5/5

Although filtering options in a tool from MOZ felt somewhat limited, they provide exclusive semantic filters and grouping.

Search volume trend*: 0/5

Does not provide ‘search volume trend’ data.

Keyword difficulty*: 5/5

Moz uses their Page authority and Domain authority metrics of the top ten pages ranking for a keyword to calculate keyword difficulty.

Their difficulty score performs really well, I must say.

SERP analysis*: 2/5

Moz provides only minimal data for the top10 search results such as PA, DA, and number of referring domains. Besides you have to do FAR too much scrolling down to see all positions.

4. SEMrush Keyword Magic Tool (13/25 points)

Number of keyword suggestions*: 4/5

Suggested: 440,273 keywords

An excellent result considering this tool (Keyword Magic) is still in Beta. However, it’s only 40% of the number of suggestions from Ahrefs.

Data filtering*: 4/5

SEMrush meets all the expectations regarding the data you’d expect to filter. Not bad at all.

Search volume trend*: 3/5

A good standard trend graph covering a period of the past 12 months. It does not show you the search volume numbers for the past months but rather gives you decimal score, where one stands for the month with the highest search volume.


 To see the search volume trend you have to leave Keyword Magic Tool and go to Keyword Analytics -> Overview section

Keyword difficulty*: 1/5

As explained in their knowledge base, SEMrush takes into consideration the authority of the domains that are showing up on the results page to determine the keyword difficulty.

In most cases, their KD score is just plain wrong (based on our experience). This is probably one of the biggest weaknesses of SEMrush as a keyword research tool in my opinion.


 I had a discussion with SEMrush team about their keyword difficulty. They acknowledge this problem and are reworking it now.

SERP analysis*: 1/5

SEMrush simply shows you a cached Google’s SERP for a given keyword with no data about the ranking pages.

5. Long Tail Pro (12/25 points)

Number of keyword suggestions*: 2/5

Suggested: 893 keywords

A reasonable number of suggestions, but due to limitations in “Max results per seed keyword” I had to run their “Google AdWords Suggestions” report multiple times.

Data filtering*: 3/5

Quite a few filtering opportunities, but the interface could probably use some improvement. As for me, it is a bit slow and clunky.

Search volume trend*: 0/5

Does not provide ‘search volume trend’ data.

Keyword difficulty*: 4/5

Keyword Competitiveness in this tool is calculated using the page title, Majestic Trust Flow and Citation Flow, links, and other factors of top 10 results found on Google.

Keyword difficulty score from Long Tail Pro was the second most accurate one after Ahrefs in our keyword difficulty test.

SERP analysis*: 3/5

Plenty of solid data. The downside of their SERP analysis is that it forces you into a new browser tab.

6. SERPStat Keyword Research Tool (10/25 points)

Number of keyword suggestions*: 3/5

Suggested: 149,003 keywords

Serpstat offered a good number of keyword suggestions. Around 35% of what SEMrush shows.

Data filtering*: 2/5

Provides some good filtering options. But you can’t filter or sort a list of suggestions by keyword difficulty.

Search volume trend*: 3/5

Leverages the power of an embed from Google Trends. Yet, it does give you an overall picture of the search term’s popularity over time.

Keyword difficulty*: ?/5

Serpstat estimates their keyword difficulty based on a number of various factors, such as backlink profiles of the top10 search results, their Page Rank and Trust Rank, and on-page factors such as keywords in title and URL.

This metric was added to Serpstat in June 2017 and I did not test it hard. So, unfortunately, I can’t give you my conclusion here.

A few words about the criteria used above

I suppose I have to add a few words about the criteria I used to grate these amazing tools: why I used exactly these and what I expected from every tool.

Number of keyword suggestions

Generally, the more keywords you have to work with, the more likely you are to find the gems.

The only fair way to compare keyword tools based on suggestions number is to run the same query through each and record the results.

I used the keyword “massage”. (That was actually one of the first words that came to mind. I could really use a massage right about now…)

The keyword suggestions count was pulled on 17 Nov 2017. And since these keyword tools regularly update their databases, you will probably get a slightly different number if you run a similar test today.

Data filtering

A huge list of keyword suggestions is only a starting point for a keyword research. Further on you need to filter this list effectively, otherwise, you’re just biting off more than you can chew.

A good keyword tool must provide easy filtering options. And no matter what other keyword metrics these tools have, search volume and keyword difficulty are a must.

Search volume trend

Now that you have some keyword gems after filtering down a list of keyword suggestions, you need to do individual keyword analysis.

It is essential to have the keyword search volume trend over time to see if the searcher’s interest is rising or fading and if seasonality influences it.

Keyword difficulty

This section requires some extra talk.

Today every good keyword research tool has some form of difficulty or competitiveness score (do not confuse it with ‘Competition’ in GKP which only applies to ads).

This metric must show you how hard it would be to rank for any given keyword. With it, you can easily filter a huge list of keyword suggestions and find those easy to rank for.

Most SEOs estimate keyword difficulty based on the backlink data of the pages in top search results. But different tools may have their own approaches.

The rates above are based on my own experience in keyword research and further ranking for many keywords. Besides, it incorporates data from our Keyword Difficulty Test.

That’s why Ahrefs gets 5/5, not just because it’s my personal favorite SEO tool.

If you still think I’m just biased towards Ahrefs, here’s another keyword difficulty study carried out by Kelvin Mah from Humanproofdesigns recently:

Which Keyword Difficulty Checker Is The Most Accurate?

Ahrefs wins there as well.

SERP analysis

This one has a lot of weight for me.

Keyword difficulty can help you narrow down your huge lists of keyword suggestions. But it won’t replace the manual review of the SERP. This is why a good keyword tool should not only give you a fairly reliable keyword difficulty score but also give you enough data to dig in once you have identified potential gems.

Why I didn’t include Google Keyword Planner (and a few other keyword research tools)

You probably noticed that Google Keyword Planner wasn’t included in my test.

This is because GKP is a specialized tool for PPC advertisers and is not really supposed to help with organic keyword research. Already back in 2012 Rand Fishkin warned us to be careful using AdWords for keyword research.

Then one day Keyword Planner started to combine search volumes for similar keywords and phrases. That move was quite reasonable for PPC keyword research, considering the Ad will be shown for any keyword in such group. But without individual search volumes, GKP became a lot less useful for organic keyword research.

But still, Google Keyword Planner can be useful and it does have a few things going for it, namely:

  • It’s free (with limitations).
  • It gives you data straight from the horse’s mouth (this is both a positive and a negative, in my opinion)

So even with the annoying search volume limitations and the fact that you can only see 700 suggestions per keyword, there is still value to be had from GKP.

(You can learn more about how to use the Google Keyword Planner in this guide from Google themselves!)

But GKP aside, you may be wondering why I didn’t include some of the other well-known keyword research tools that scrape Google autocomplete and “related searches,” such as:

In all honesty, I did not test such tools because the number of suggestions they give is insufficient and because they usually don’t provide any “statistics” about the keywords they spit out. They might be fun to work with and helpful in some cases, but I don’t think they fall into “professional tools” category.

Final thoughts

You saw the results of my test. However, there are more things to consider when picking a keyword research tool. All in all, your choice must depend on the level of your SEO knowledge and the job you’re looking to accomplish.

Ahrefs is a tool for experienced SEOs who will make use of every detail they can get, while KWfinder is a perfect choice for someone who’s just starting out, considering its money/value ratio.

I’m a long-time user of Ahrefs, so it may seem that I’m biased. But, in all honesty, I love my business and my bank account more than any SEO brand. So if some other tool will help me better than Ahrefs, I’ll switch immediately.

How useful was this post?

Leave a Reply

Your email address will not be published. Required fields are marked *

SeoToolBuy Content Protected