Keyword Research API: 9 SEO Data APIs Compared (2026)

A keyword research API returns search volume, cost per click, keyword difficulty and keyword ideas as JSON, so a script, a dashboard or an AI agent can do keyword research without anyone opening a tool. This comparison covers nine keyword and SEO data APIs: what each one returns, the entry price shown on the vendor's own page on 8 and 9 November 2026, and the unit each one bills in, which is where the real cost hides.

The 9 keyword research APIs at a glance

API	Good fit for	Entry price	Usage counted in
Arvow	Keyword research that feeds content, from code or an AI agent	From $39 a month billed yearly ($69 billed monthly)	Credits: 1 to 3 per call
DataForSEO	Bulk keyword data, pay as you go	$50 minimum top-up	Tasks: $0.06 for up to 1,000 keywords
Google Ads API	Keyword Planner numbers from Google itself	Access by application	Operations per day, by access level
SE Ranking	A broad SEO data API with a prepaid wallet	€45 for 250,000 credits	Credits per request or per record
Semrush	Teams already on the Semrush Business tier	Add-on, no price on the page	API units per line
Ahrefs	Teams already paying for Ahrefs	Lite plan, €119 a month	API units, at least 50 per request
Moz	Small volumes on a fixed monthly bill	Free for 50 rows a month, then from $20 a month	Rows
Keywords Everywhere	Low-cost volume and CPC lookups	$7 a month billed annually ($84)	Credits: 1 per keyword
kwrds.ai	Low call counts with People Also Ask data	$49 a month	API calls: 600 a month

SE Ranking and Ahrefs showed euro prices to a visitor in Portugal, so they are quoted in euros. Every other price is in US dollars as listed.

What a keyword research API returns

Most keyword APIs offer the same four kinds of call under different names: metrics for keywords you already have (volume, CPC, competition, difficulty), ideas from a seed term, the pages ranking for a query, and domain data such as the keywords a site ranks for. That last group is where a keyword API becomes an SEO data API, and most products here are SEO data APIs with keyword endpoints inside them.

Before you compare prices, check three things: the unit you are billed in (keywords, rows, calls, credits or tasks), how many keywords fit in one call, and whether unused credits expire.

The nine APIs

1. Arvow API: keyword research next to the content it feeds

Arvow is a content automation platform, and its REST API includes ten SEO Research operations, listed in the API reference. The keyword overview call returns search volume, CPC, competition, difficulty and search intent for a batch of 1 to 20 keywords and costs 1 credit. Keyword ideas, related keywords and long-tail suggestions cost 2 credits a call and return up to 50 rows. A SERP call returns up to 20 organic results for 1 credit. Domain calls cover a domain overview, ranking keywords and competing domains at 2 credits each, plus keyword gaps and a backlink overview at 3 credits each.

A keyword lookup is one request:

• Host: https://api.arvow.com
• Request: POST /api/v0.1/projects/{projectId} followed by /seo/keywords/overview
• Header: Authorization: Bearer YOUR_API_KEY
• Body: {"keywords": ["keyword research api", "seo data api"], "countryCode": "us"}

The same operations are tools on the Arvow MCP server, so ChatGPT, Claude or a coding agent can research keywords, then write and publish the article in the same session. The pricing page lists API Access and MCP Access from the Solo plan: $39 a month billed yearly, or $69 billed monthly, with 1,000 credits a month.

Limits: every call runs under a project, so you need an Arvow project ID. Batches stop at 20 keywords and lists at 50 rows, the response carries no monthly trend history, and research calls draw on the same credits as articles, which cost 15 credits each. It is built for research that feeds content, not for bulk data pulls.

2. DataForSEO: pay as you go, priced per task

DataForSEO's Keyword Data API returns Google Ads keyword data at $0.06 per task in the standard queue, with a turnaround of up to 45 minutes, or $0.09 per task in live mode. A task holds up to 1,000 keywords, which the vendor's table works out to $60 or $90 per million keywords. The DataForSEO Labs API adds keyword research, search intent and competitor endpoints at $0.012 per task plus $0.00012 per item. The pricing page sets a $50 minimum top-up, says the balance never expires and gives new accounts $1 of trial credit.

Limits: prices differ by endpoint and by queue or live mode, so estimate the cost per endpoint before you build on it.

3. Google Ads API: Keyword Planner data from the source

Google's KeywordPlanIdeaService generates keyword ideas, historical metrics and forecast metrics. The historical metrics call takes up to 10,000 keywords per request and returns average monthly searches, monthly volumes for up to four years, a competition level and index, and top-of-page bid ranges. Access is set per Google Cloud project by access level: Explorer access allows 2,880 operations a day on production accounts, Basic allows 15,000 and Standard is unlimited.

Limits: you apply for access, and your permissible use decides which features you get. Keyword planning requests have stricter rate limits than the rest of the API, and the metrics are advertising metrics: the list above has no organic difficulty score.

4. SE Ranking API: a wallet you top up, with an MCP server

SE Ranking's SEO API has a Keyword Research API alongside backlink, domain, audit and AI search endpoints, and the page cites a database of 5.5 billion keywords across 188 countries. The API pricing page lists a 14-day trial with 100,000 credits, a Wallet at €45 for 250,000 credits that never expire, and a Standalone plan at €155 a month, billed annually, for 12 million credits a year. Existing subscribers can add the API from €39 a month on annual billing. MCP access is included in every option.

Limits: some endpoints charge credits per request and others per record returned. Credits on annual plans expire at the end of the billing cycle.

5. Semrush API: an add-on for the Business tier

Semrush's knowledge base describes the standard API as an add-on to the Business tier of the SEO Toolkit subscription. After upgrading you buy API units in packages of 2, 5, 10 or 20 million, and each call costs units by request type or by lines returned. Unused units expire at renewal. The page gives no price for the units.

Limits: it only makes sense if you are on, or moving to, the Business tier. Check the unit cost of each report before you automate it.

6. Ahrefs API: Keywords Explorer data on your Ahrefs plan

The Ahrefs API exposes Keywords Explorer: metrics for one keyword or a list, search volume history, volume by country and keyword ideas. The pricing page lists API and MCP access on the Lite (€119 a month), Standard (€229) and Advanced (€419) plans, with 100, 250 and 500 rows per request. Requests consume API units, the minimum cost of a request is 50 units, and the default rate limit is 60 requests a minute.

Limits: the unit cost depends on the rows and fields you request, so trim the fields. Test queries that consume no units are available for development.

7. Moz API: billed in rows, with a free tier

The Moz API includes keyword data with search intent alongside its link data. The pricing page counts usage in rows. The free tier allows one request every ten seconds and up to 50 rows a month. Paid plans start at $20 a month for 3,000 rows and $75 for 15,000, then $125 for 50,000, $250 for 120,000 and $500 for 500,000. MCP access is listed as a beta on the paid plans.

Limits: the endpoint and its parameters decide how many rows a call uses, and the $20 plan has no overage option, so a busy month means moving up a plan.

8. Keywords Everywhere API: one credit per keyword

Keywords Everywhere says in its API documentation that all API methods are available on every subscription plan, including Bronze, the entry plan, and that the API can also be reached through an MCP server. The pricing page starts at $7 a month, billed annually at $84, for 100,000 credits a year, and goes up to $120 a month for 8 million. One credit returns volume, CPC, competition and 12-month trend data for one keyword.

Limits: credits expire after one year, and the browser extension spends the same credits.

9. kwrds.ai API: a fixed number of calls a month

The kwrds.ai API offers keyword research, search volume, People Also Ask and SERP endpoints. Its Starter plan is $49 a month for 600 API calls, capped at 20 a day, and the Full plan is $99 a month for 1,200 calls, capped at 40 a day. A free plan allows one call per endpoint for testing.

Limits: the daily caps make it a fit for a small tool or a weekly report, not for bulk pulls.

What Google's data rules mean for any keyword API

Google's documentation sets two facts that matter whichever API you buy. First, historical search volume refreshes monthly, and Google recommends caching keyword planning results. Asking for the same keyword every day buys nothing: store the result and refresh it monthly. Second, direct access is an application with daily operation limits and a stated permissible use. That is the trade-off against buying from a data vendor.

How to choose a keyword research API

• Research that ends in a published article, from code or an AI assistant: Arvow, because research, writing and publishing sit behind one key.
• Large volumes at a known unit price: DataForSEO, billed per task with no subscription.
• Google's own numbers: the Google Ads API, if you can live with the application and the limits.
• You already pay for Semrush, Ahrefs or SE Ranking: use the API on that plan first.
• A few thousand lookups a month: Moz from $20, Keywords Everywhere from $7 billed annually, or kwrds.ai for People Also Ask data.

FAQ

What is a keyword research API?

A keyword research API is a web service that returns keyword data, such as search volume, CPC, difficulty and related keyword ideas, in a machine-readable format. You send keywords or a seed term and get the metrics back as JSON.

Is there a free keyword research API?

A few have a small free allowance. Moz allows up to 50 rows a month, kwrds.ai allows one call per endpoint, SE Ranking runs a 14-day trial with 100,000 credits, and DataForSEO gives new accounts $1 of trial credit. Arvow has no such tier: API access starts on the Solo plan.

Can I use a keyword research API from ChatGPT or Claude?

Yes, through an MCP server. Arvow, SE Ranking, Ahrefs and Keywords Everywhere each document one, Moz lists MCP access as a beta, and DataForSEO mentions MCP access on its pricing page. With the Arvow MCP server connected, you ask for keyword metrics in plain language and the assistant makes the call.

What does a keyword volume API cost per keyword?

It depends on the billing unit. DataForSEO's standard queue works out to $0.06 per 1,000 keywords. Keywords Everywhere charges one credit per keyword, and its entry plan is $84 a year for 100,000 credits. Arvow's keyword overview call costs 1 credit for up to 20 keywords. The other vendors bill in rows, units or calls, so compare them on a sample of your own requests.