8 Best Keyword Research Tools for Agencies in 2026

Prices, limits and database figures come from each vendor's own pricing, feature and help pages, checked on 12 October 2026, and are 'as of October 2026'. Database sizes are as each vendor states them and are counted differently, so they are not directly comparable. Mangools and AnswerThePublic may show prices adjusted for your location; we say where that applies.

What agencies need from a keyword tool

• Coverage in your clients' countries and languages, tested on their real niches during a trial.
• Daily limits that survive a busy week: reports per day, rows per report, export rows.
• Seats: most suites include one user and charge for the rest.
• Grouping: clustering or keyword lists that turn thousands of keywords into page plans.
• An API or MCP access if you build your own reports or feed an AI assistant.

At a glance (as of October 2026)

The tools, one by one

Semrush: the broadest database

Semrush states more than 28 billion keywords across 142 geographic databases. The SEO plan ($139 a month, $117.33 billed annually) allows 3,000 reports a day with 10,000 results per report and 250 keyword metric updates a month; Pro+ ($299) raises that to 5,000 reports, 30,000 results and 1,000 updates, and Advanced ($549) to 10,000 reports, 50,000 results and API access. Keyword Strategy Builder groups keywords into topic clusters by comparing top-10 results. Each plan includes one user; extra users cost $45 to $100 a month by plan. 7-day trial with exports disabled. Best for: agencies researching many markets. Limit: seats and reports are priced separately.

Ahrefs: strong data, credit limits

Ahrefs states 28.7 billion keywords filtered from 110 billion discovered, across 217 locations. Lite ($129 a month) gives one user 1,000 credits a month and 2,500 rows per report; Standard ($249) removes the credit cap and allows 30,000 rows, and adds keyword clusters by parent topic; Advanced ($449) allows 75,000 rows. Extra users are $40 to $100 a month. API and MCP access are on every paid plan from Lite. Starter ($29) covers light lookups with 200 credits a month. No trial. Best for: agencies that also rely on Ahrefs for links. Limit: Lite's credit cap is low for keyword-heavy work.

SE Ranking: most projects per dollar

SE Ranking states 5.5 billion keywords across 188 locations (one page also says 5.4 billion). Core ($129 a month, $103.20 billed annually) includes 10 projects, 50,000 export rows, 25,000 API credits, MCP access and a keyword grouper priced per query; extra seats start at $16. Its own FAQ says its search volume figures currently trail Semrush's and Ahrefs'. 14-day trial without a card. Best for: agencies with many small clients. Limit: check volumes against a second source for important keywords.

Serpstat: budget suite with clustering

Individual ($69 a month, $50 billed annually) allows 100 searches a day and 50,000 export rows; Team ($129, or $100 annually) 500 searches a day, 3 users and the API. Keyword clustering costs 5 credits a keyword from shared tool credits (5,000 a month on Individual), with up to 50,000 keywords per project. Serpstat's pages give three different database sizes. 7-day trial with a $1 card verification. Best for: small agencies that cluster keyword lists regularly. Limit: credits are shared across several tools.

Mangools KWFinder: simple, with daily limits

KWFinder is part of the Mangools bundle. Basic allows 100 keyword lookups per 24 hours, Premium 500 and Agency 1,200; Premium and Agency add seats that share the account's limits. Mangools states 2.5 billion related keywords and about 65,000 locations, but its search-by-domain feature covers 17 countries. Prices are adjusted by visitor location; annual billing saves up to 35%. Free plan with 5 lookups per 24 hours, and a full refund within 48 hours of payment. Best for: freelancers and small teams. Limit: competitor-domain research covers 17 countries.

Keywords Everywhere: volumes while you browse

Annual plans from $84 (Bronze, 100,000 credits, 1 seat) to $1,440 (Platinum, 8 million credits, 20 seats) add volume, CPC and competition to Google and other sites. One credit is one keyword, credits expire after a year, and the API uses the same credits. For country-level data it lists Global plus a handful of countries, mostly English-speaking (the US, UK, Canada, Australia, New Zealand, South Africa and India). Best for: writers and strategists who need volumes on the fly. Limit: no rank tracking or project management.

AnswerThePublic: the questions people ask

AnswerThePublic, part of NP Digital, turns a keyword or URL into the questions and phrases people use across Google, YouTube, Amazon, ChatGPT and more, grouped into questions, prepositions, comparisons and related terms, and now adds AI prompt suggestions and AI drafting. The yearly-billed plans shown to us were Starter at $6.66 a month (1 user, 100 searches a month), Growth at $32.66 (3 users, 200 searches) and Business at $66 (10 users, 300 searches); we could not confirm monthly-billed prices, and its sister product Ubersuggest prices by region. A small number of free searches a day is available. Best for: building FAQ sections and question-led content plans. Limit: searches are capped per month.

Google Keyword Planner: free, for advertisers

Keyword Planner is free inside Google Ads once the account setup, including billing information, is complete and the account is in Expert Mode. Google says historical average monthly searches are shown only for exact matches and that very low-volume keywords are not shown. Best for: checking volumes against Google's own data. Limit: needs an Ads account and shows no competitor data.

Pick by agency size

Keywords versus prompts

Keyword tools measure what people type into Google. Buyers also ask assistants longer questions that never show up as search volume. Fenn's keyword research is in development and not part of any plan yet. What it does today is ask ChatGPT, Claude, Gemini, Perplexity and Grok the questions your clients' buyers ask, show who gets named, and turn questions from the subreddits, YouTube channels and competitor blogs you choose into answer-first drafts that mark the facts only the client can supply. Use a keyword tool for search demand and a prompt set for AI answers. Plans start at $29 a month, set up after a demo.

FAQ

What is the best keyword research tool for agencies?

As of October 2026, Semrush has the largest stated database and highest report limits per plan, SE Ranking gives the most client projects per dollar, and Ahrefs suits agencies that also want its link data. Trial two on your clients' real niches before choosing.

What is the best free keyword research tool?

Google Keyword Planner (free with a Google Ads account), Semrush's free plan (10 reports a day), Mangools' free plan (5 lookups a day) and a few free AnswerThePublic searches a day.

Which keyword tool has an API on its entry plan?

SE Ranking includes 25,000 API credits on Core and Ahrefs includes API and MCP access from Lite. Semrush lists API access on Advanced, and Serpstat from Team.

Do keyword tools show AI search demand?

Not directly. Search volume counts Google searches, not questions asked in assistants. Some tools now suggest AI prompts (AnswerThePublic) or track brand mentions in AI answers (Semrush, SE Ranking, Ahrefs Brand Radar).