Best Keyword Clustering Tools in 2026: 9 Grouping Tools Compared

You have a spreadsheet of a few thousand keywords and one question: which of them can share a page? A keyword clustering tool answers it by grouping the list, and a keyword grouping tool does the same job under a different name. Get it wrong and you write five posts that compete with each other, or one post that tries to cover five different intents.

Tools differ in two ways that matter: how they decide two keywords belong together, and how they charge for it.

SERP-based versus semantic clustering

SERP-based clustering pulls the top results for each keyword and groups keywords whose results share enough URLs. If Google ranks the same pages for two queries, one page can probably serve both. Most tools below work this way and let you set the threshold. LowFruits groups keywords that share at least 40% of their top-10 URLs by default. Keyword Insights’ pages quote 30% in one place and 40% in another. Serpstat asks for 3, 8 or 12 shared URLs in the top 30 (weak, medium or strong). Each keyword needs a live results pull, which is why these tools meter by keyword or credit.

Semantic (NLP) clustering groups keywords by meaning or shared words without checking Google. It’s fast and cheap, and it suits exploring a niche, but it can’t tell you whether Google treats two phrasings as the same intent. LowFruits has a semantic mode that groups by shared words (you choose how many). Ahrefs’s “Cluster by terms” tab groups by common words and phrases. Keyword Insights says it uses NLP only to relate finished clusters to each other, not to form them.

Parent Topic clustering is Ahrefs’ own method: it groups keywords by the keyword that sends the most traffic to the top-ranking page. Ahrefs says that’s why it’s instant, and in a 2023 test on its blog more than half of its top 25 clusters matched a SERP-based tool’s output. Ahrefs also says clustering results are never perfect and are open to interpretation, so review clusters by eye before you write.

The tools

1. Keyword Insights: clustering is the whole product

It pulls live, country-specific results and clusters on URL overlap, with a threshold you can change. It can add your current rank and ranking URL to each cluster, show competitor visibility, and send a cluster to a content brief. It says it handles up to 200,000 keywords at a time.

Clustering costs 1 credit per keyword. Basic is $58/month for 10,000 credits and one seat ($46/month billed annually). Professional is $99/month for 20,000 credits and three seats. Pay as you go is $110 for 10,000 credits, valid 30 days and clustering only. A $1, 7-day trial gives 5,000 credits. Unused monthly credits reset, and all credits are removed if you cancel.

2. Semrush Keyword Strategy Builder: topics and pillar pages

Enter up to five seed keywords or import a list, and it groups keywords into topics, pillar pages and subpages. Semrush says it clusters on SERP overlap, not word similarity. It analyzes up to 10,000 keywords, and you can upload 2,000 at a time. You can send a cluster straight to Semrush’s writing tools.

Semrush’s help page says it’s included with paid SEO Toolkit subscriptions, which started at $139/month ($117.33 billed annually) with a 7-day trial. The pricing table doesn’t list it by name, so confirm on your plan. Semrush warns that a cluster’s KD% is an average that can hide a hard primary keyword.

3. SE Ranking Keyword Grouper: pay per keyword

You pick country, language, the minimum number of matching URLs and a clustering method, and can optionally check search volume. SE Ranking’s blog says it’s for paid subscribers and costs $0.004 per query, plus $0.005 for the search-volume check.

The subscription is separate: Core is $129/month, or $103.20 billed annually, with a 14-day free trial. Neither the tool page nor the pricing page states a maximum list size, and the usage fees stack on top of the subscription.

4. Ahrefs: instant clusters, no upload

Paste a list or run a keyword report in Keywords Explorer and click “Clusters by Parent Topic”. There’s no waiting. A “Cluster by terms” tab groups by shared words, and a SERP comparison scores how similar two keywords’ results are out of 100.

Ahrefs’s pricing page lists keyword clusters from the Standard plan: $249/month, or $208/month billed yearly. Lite is $129. It’s a full SEO suite, so it’s poor value if clustering is your only job, and Parent Topic grouping isn’t the same as URL-overlap clustering.

5. LowFruits: SERP or semantic, your choice

LowFruits clusters either by SERP overlap or by shared words. It clusters keywords whose results you’ve already analyzed, and each analyzed keyword costs 1 credit, so there’s no separate clustering fee on the pricing page. Standard is $29.90/month ($20.75 billed yearly) for 3,000 credits. Premium is $79.90 for 10,000. Pay-as-you-go packs run from $25 for 2,000 credits. Credits expire after a year, and there’s a 14-day money-back guarantee if you’ve used under 100 credits.

Monthly credits don’t roll over.

6. Keyword Cupid: cheap, SERP-based, pay by keyword

Keyword Cupid describes itself as a SERP-based clustering and grouping platform. Starter is $9.99/month for 500 keyword credits and up to 2,000 keywords per report. Freelancer is $49.99 for 5,000 credits, Agency $149.99 for 20,000 and Enterprise $499.99 for 80,000. Extra credits cost $0.020, $0.010, $0.007 and $0.006 per keyword by plan, and they don’t expire. Reports include a mindmap and Excel export.

Starter’s 500 credits cover one small list a month, and extra credits need a subscription.

7. Serpstat: strictness settings for large lists

Serpstat’s help page describes SERP-based clusters from 3 to 50,000 keywords per project. You choose strength (3, 8 or 12 shared URLs in the top 30) and soft or hard grouping, and adding your domain assigns the best-matching page to each cluster.

Clustering costs 5 credits per keyword from a pool shared with text and batch analysis. The Individual plan has 5,000 tools credits, roughly 1,000 keywords a month, at $69/month monthly or $50 billed annually. Bigger lists need a plan with more credits (Team has 25,000), and Serpstat lists a free trial.

8. ContentGecko: a free first run

ContentGecko’s tool fetches Google’s top 10 for each keyword and groups by a minimum overlap you set (1 to 10 shared URLs). Free covers 200 keywords. The paid plan is €19.90/month for 50,000 keyword credits and up to 20,000 keywords per run, plus intent, page-type and funnel-stage labels.

ContentGecko’s main product is an automated blog for ecommerce stores, starting at €437/month. The clustering plan is separate, and the free version uses a slower algorithm.

9. WriterZen: pay once

WriterZen sells lifetime plans rather than subscriptions. Its Keyword Planner imports up to 20,000 keywords and clusters “by SERPs”, with intent and buying-journey views. On the main pricing page, Keyword Research is $135 one-time (50,000 keyword credits, 10,000 keywords clustering), All-In-One Basic $270 and Advanced $405. A promo page listed $75, $150 and $225 with lower credits. Extra keyword credits start at $19 for 10,000. There’s a 21-day money-back guarantee.

Prices differ by page version, and credits are finite.

Quick comparison

How to choose

1. Match the method to the job. To decide which keywords share a page, use a SERP-based tool. To explore a niche or spot patterns in a huge list, a word-based view (LowFruits’ semantic mode, Ahrefs’ terms tab) is faster.
2. Price your actual list. Using the stated rates, 10,000 keywords works out to about $58 on Keyword Insights Basic, $40 in SE Ranking usage fees on top of the subscription, or $100 of LowFruits pay-as-you-go credits for the SERP analysis.
3. Test built-in clustering first. If you already pay for Semrush or Ahrefs, run a real list through their clusters before adding another tool.
4. Check list limits, exports and settings. Keyword Cupid’s per-report caps, Serpstat’s 50,000 and Semrush’s 2,000-per-upload limit all change how you work.
5. Plan the next step. Clusters become briefs, so check how each tool hands off. Keyword Insights sends a cluster to a brief, and our Frase alternatives and Surfer SEO alternatives guides cover the editors that come after.