Quick answer: Semrush ranks #1 at 87/100 because topic research is fundamentally a data problem — the bigger and cleaner the keyword and topic database, the better your prioritization — and Semrush’s 27-billion-keyword index plus its Topic Research tool is the deepest here. AlsoAsked is the runner-up at 84: it does one thing, mapping the “People Also Ask” tree, and does it sharply for a fraction of the price. If you mainly need to brainstorm cheaply, AnswerThePublic at $11/mo is the budget answer.
We split the field into two jobs — broad data-driven discovery and question-structure mining — and scored across both, weighting toward whether the output actually reflects what people search.
The ranking
| Rank | Tool | Best for | Entry price (monthly) | SR Score |
|---|---|---|---|---|
| 1 | Semrush (Topic Research + Keyword Magic) | Deepest combined data | $139.95 (Pro) / $249.95 (Guru) | 87 |
| 2 | AlsoAsked | ”People Also Ask” mapping | $12 (Basic) | 84 |
| 3 | MarketMuse | Topical-authority planning | $99 (Optimize); free tier | 83 |
| 4 | AnswerThePublic | Visual brainstorming | $11 (Individual) | 80 |
| 5 | Frase | Research + brief in one | $49 (Starter) | 79 |
| 6 | Scalenut | Cluster/keyword planning | $59 (Starter) | 76 |
Methodology
| Criterion | Weight | What we measured |
|---|---|---|
| Evidence & testing | 30 | Does the output reflect real search demand — accurate volume, live PAA, genuine related topics? |
| Capability vs. claims | 25 | Breadth: subtopics, questions, clustering, volume/difficulty, intent. |
| Value for money | 20 | Cost vs. depth at the entry plan; search/credit limits. |
| Support & docs | 15 | Onboarding, exports, integrations. |
| Transparency | 10 | Clear pricing, search/credit limits, which tier a feature needs. |
Evidence leads because the whole point is to chase real demand. We dinged tools that surface ideas without any demand signal, and tools that bury the research feature behind a surprise tier.
Profiles
1. Semrush — 87
Keyword Magic Tool draws on 27.3B+ keywords with volume, difficulty, and intent; the Topic Research tool turns a seed term into topic cards, headlines, and questions. Pro $139.95/mo (Keyword Magic), Guru $249.95/mo (Topic Research + Content Toolkit), Business $499.95/mo.
| Criterion | Score | Weight | Contribution |
|---|---|---|---|
| Evidence & testing | 92 | 30 | 27.6 |
| Capability vs. claims | 90 | 25 | 22.5 |
| Value for money | 74 | 20 | 14.8 |
| Support & docs | 88 | 15 | 13.2 |
| Transparency | 80 | 10 | 8.0 |
| Total | 100 | 86.1→87 |
Trade-off: the full Topic Research tool requires Guru ($249.95). Overkill if all you want is question mining — that is exactly where AlsoAsked wins.
2. AlsoAsked — 84
Purpose-built around Google’s “People Also Ask” — it renders the live PAA tree so you see how questions branch. Basic $12/mo (100 credits), Lite $23/mo (300), Pro $47/mo (1,000); 3 free searches/day.
| Criterion | Score | Weight | Contribution |
|---|---|---|---|
| Evidence & testing | 86 | 30 | 25.8 |
| Capability vs. claims | 78 | 25 | 19.5 |
| Value for money | 92 | 20 | 18.4 |
| Support & docs | 78 | 15 | 11.7 |
| Transparency | 88 | 10 | 8.8 |
| Total | 100 | 84.2→84 |
Trade-off: it does PAA and little else — no volume data, no clustering beyond questions. Within its lane it is the best value here.
3. MarketMuse — 83
Builds topic models that show which subtopics you must cover to own a theme. Free (10 queries), Optimize $99/mo, Research $249/mo.
| Criterion | Score | Weight | Contribution |
|---|---|---|---|
| Evidence & testing | 86 | 30 | 25.8 |
| Capability vs. claims | 86 | 25 | 21.5 |
| Value for money | 76 | 20 | 15.2 |
| Support & docs | 80 | 15 | 12.0 |
| Transparency | 84 | 10 | 8.4 |
| Total | 100 | 82.9→83 |
Trade-off: oriented to authority strategy rather than raw idea volume; best for planning hubs.
4. AnswerThePublic — 80
The visual search-listening classic — a seed keyword fans into questions, prepositions, and comparisons. Individual $11/mo (100 searches/day; ~$7 annual), Pro $99/mo (unlimited), Expert $199/mo; 3 free searches/day.
| Criterion | Score | Weight | Contribution |
|---|---|---|---|
| Evidence & testing | 78 | 30 | 23.4 |
| Capability vs. claims | 74 | 25 | 18.5 |
| Value for money | 90 | 20 | 18.0 |
| Support & docs | 78 | 15 | 11.7 |
| Transparency | 86 | 10 | 8.6 |
| Total | 100 | 80.2 |
Trade-off: brainstorming gold, but autocomplete-derived ideas lack reliable volume/difficulty data — pair it with a keyword tool before committing.
5. Frase — 79
Bundles SERP research and topic discovery into the brief workflow. Starter $49/mo, Professional ~$98/mo.
| Criterion | Score | Weight | Contribution |
|---|---|---|---|
| Evidence & testing | 78 | 30 | 23.4 |
| Capability vs. claims | 78 | 25 | 19.5 |
| Value for money | 84 | 20 | 16.8 |
| Support & docs | 78 | 15 | 11.7 |
| Transparency | 80 | 10 | 8.0 |
| Total | 100 | 79.4 |
Trade-off: research is a means to its brief, not a standalone discovery engine. Strong if you research and write in one place.
6. Scalenut — 76
Cluster and keyword planning feed its drafting workflow. Starter $59/mo, Plus $89/mo, Professional $199/mo.
| Criterion | Score | Weight | Contribution |
|---|---|---|---|
| Evidence & testing | 76 | 30 | 22.8 |
| Capability vs. claims | 76 | 25 | 19.0 |
| Value for money | 80 | 20 | 16.0 |
| Support & docs | 74 | 15 | 11.1 |
| Transparency | 78 | 10 | 7.8 |
| Total | 100 | 76.7 |
Trade-off: clustering is decent but secondary to its writing focus.
Verification
- Semrush — Pro $139.95 / Guru $249.95 / Business $499.95; Keyword Magic (27.3B+ keywords) and Topic Research tier placement verified via semrush.com and 2026 pricing pages.
- AlsoAsked — Basic $12 / Lite $23 / Pro $47, 3 free/day verified on alsoasked.com/pricing.
- MarketMuse — free 10 queries + Optimize $99 / Research $249 verified on marketmuse.com/pricing.
- AnswerThePublic — Individual $11 / Pro $99 / Expert $199, 3 free/day verified on answerthepublic.com/en/pricing.
- Frase — Starter $49 / Professional ~$98 verified on frase.io/pricing.
- Scalenut — Starter $59 / Plus $89 / Professional $199 verified on scalenut.com/pricing.
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Frequently asked questions
- What is a topic research tool?
- It helps you discover what to write about — expanding a seed keyword into subtopics, questions, related searches, and content ideas, often with search-volume and difficulty data so you can prioritize. It answers 'what should this cluster cover?' before you brief or write.
- Which topic research tool is best?
- Semrush for the deepest combined keyword + topic data; AlsoAsked when you specifically want to map the questions real users ask. AnswerThePublic is the cheapest way to brainstorm visually. Pick based on whether you need volume data or question structure.
- Can I do topic research for free?
- Yes, partly. AnswerThePublic and AlsoAsked both offer 3 free searches per day, Google's autocomplete and 'People also ask' are free, and Semrush's Keyword Magic has a limited free tool. Volume work needs a paid plan.
- What's the difference between topic research and keyword research?
- Keyword research finds individual query strings and their volume. Topic research clusters those into themes and questions so you can plan whole content hubs, not just single pages. Modern tools blend both.
- Does Semrush's Topic Research need a paid plan?
- The Topic Research tool sits in the Content Marketing Toolkit, which unlocks at the Guru tier ($249.95/mo). Keyword Magic Tool is available from the Pro tier ($139.95/mo) and in a limited free version.