How we make this list: we compare pricing pages, product documentation and public user reviews. Rankite is independent; if a vendor ever pays for a featured spot, that listing is clearly labeled Partner.
Key takeaways
- DataForSEO is the cheapest route to bulk keyword data if you have a developer who can handle raw API plumbing.
- Ahrefs and Semrush APIs only make financial sense when you already pay for the suites, since the subscription is the real entry ticket.
- SerpApi is the friendliest starting point for clean SERP and keyword JSON at low volume, with a real free tier.
- Keywords Everywhere and Keyword Tool APIs cover the niches the big suites price awkwardly: cheap volume lookups and autocomplete data from platforms like YouTube, Amazon and TikTok.
Quick comparison
| Tool | Best for | Starting price | Free plan |
|---|
 DataForSEO | high-volume keyword data on a prepaid balance | $50 minimum top-up, pay as you go (Keywords Data API from $0.0012 per task) | No (one-time $1 trial credit) |
 Ahrefs API | teams already paying for Ahrefs that want its link index in code | $129/month (Lite plan, 200,000 integration units) | No |
 Semrush API | enterprises already paying for Semrush that need programmatic access | $549/month (Advanced plan) plus separately billed API units | No |
 SerpApi | developers who want clean SERP JSON fast | $25/month (Starter, 1,000 searches) | Yes (250 searches per month) |
 Keyword Tool API | autocomplete keyword ideas from YouTube, Amazon, TikTok and more | $68/month (Starter, 50 requests per day) | No (30-day money-back guarantee) |
 Keywords Everywhere API | cheap volume, CPC and competition lookups in scripts | $84/year (Bronze, 100,000 credits) | Free API key (credits required for data calls) |
 Moz API | teams that need Domain Authority in their own tools | $20/month (Starter API, 3,000 rows) | Yes (50 rows per month) |
 Serpstat API | agencies piping Serpstat data into their own reports | $100/month (Team plan, API included) | Free trial (7 days) |
 Mangools API | small teams that want KWFinder data in internal dashboards | $129/month (Agency plan, $89.90 billed annually) | Free trial (10 days) |
 ValueSERP | budget SERP data at scale | $50/month (25,000 credits) | Free trial |
Is your product missing or out of date?
We review this list regularly. Vendors can request a listing, send updated pricing or ask about featured placement.
Starting price$50 minimum top-up, pay as you go (Keywords Data API from $0.0012 per task)
Free planNo (one-time $1 trial credit)
DataForSEO does not sell you software. It sells data by the request, and for keyword research that means the Keywords Data API (search volume, trends and ad data from Google Ads, Google Trends and Bing Ads) plus the DataForSEO Labs API for keyword, competitor and market intelligence. There is no subscription or monthly reset. You top up a minimum of $50, spend it at your own pace, and the balance never expires.
The honest catch is that this is infrastructure, not a product. Responses arrive as structured JSON, error handling is your job, and billing changes with the endpoint and the parameters you send. A sandbox plus a $1 trial credit lets you test before spending real money, and the dashboard includes spending limits so a runaway script cannot drain the balance overnight.
What we like- Lowest per-keyword rates at real volume
- Huge endpoint library beyond keywords
- Balance never expires
Watch out for- Raw JSON with no dashboard
- Per-endpoint billing units take study
#2
Ahrefs API
Best for: teams already paying for Ahrefs that want its link index in code
Visit ahrefs.com
Starting price$129/month (Lite plan, 200,000 integration units)
Free planNo
The Ahrefs API exists to put the Ahrefs database inside your own tools, and its strongest card is the backlink index, still the largest most SEO teams will touch. Keyword data comes with it, but many buyers come for Domain Rating and referring-domain counts they can pipe into prospecting sheets or dashboards. Direct API v3, the Ahrefs MCP server and Ahrefs Connect all draw from the same monthly integration allowance.
That allowance is the part to budget carefully. Every request costs at least 50 units, and rows and requested fields add more, so a sloppy script that pulls full backlink profiles can eat a Lite plan's 200,000 units quickly. Row caps rise with the tier: 100 per request on Lite, 250 on Standard and 500 on Advanced.
What we like- DR and UR are the metrics clients already trust
- Batch endpoints for domain analysis
- MCP server included
Watch out for- Units burn fast on row-heavy calls
- No rank tracking endpoints
#3
Semrush API
Best for: enterprises already paying for Semrush that need programmatic access
Visit semrush.com
Starting price$549/month (Advanced plan) plus separately billed API units
Free planNo
Semrush splits its API into a Standard/Analytics track for SEO and PPC data and a separate Trends API, and both sit behind a paywall that starts with the subscription. API access sits on the Advanced plan at $549 a month ($455.67 billed annually), and the unit balance starts at zero after upgrading. Units are bought separately, cost different amounts per request type, and are not published, so get a quote from sales before scoping a build.
For the right buyer this is still the richest dataset available: roughly 26 billion keywords, 43 trillion backlinks and 142 geo databases, plus years of historical data. The honest math is that this API extends a Semrush investment rather than founding a new one.
What we like- The largest keyword database of any suite here
- PPC, traffic and backlink data in one place
- Daily position updates
Watch out for- The plan only buys permission, units cost extra
- Unit pricing is not published
Starting price$25/month (Starter, 1,000 searches)
Free planYes (250 searches per month)
SerpApi is the API most developers reach for first, and the reason is how little friction stands between signup and a working integration. One key covers Google, Bing, Baidu, DuckDuckGo, YouTube, Google Maps and more, with structured JSON for organic results, ads, knowledge panels and People Also Ask boxes, plus location and device targeting. Docs are strong, SDKs cover the common languages, and a playground lets you test queries before writing code.
The pricing is simple to the point of being blunt. The free tier gives 250 searches a month with no card required, then $25 for 1,000, $75 for 5,000, $150 for 15,000 and $275 for 30,000, with larger tiers above. Every search counts the same whether it returns 100 results or none, and unused searches reset monthly. At real scale, DataForSEO undercuts it substantially.
What we like- Excellent documentation and playground
- 20 plus search engines
- SOC 2 Type II certified
Watch out for- Unused monthly credits expire
- Costs scale linearly at high volume
#5
Keyword Tool API
Best for: autocomplete keyword ideas from YouTube, Amazon, TikTok and more
Visit keywordtool.io
Starting price$68/month (Starter, 50 requests per day)
Free planNo (30-day money-back guarantee)
Keyword Tool earns its place because it covers surfaces no official API touches. Its autocomplete engine pulls suggestions from 16 platforms, Google, YouTube, Bing, Amazon, eBay, App Store, Play Store, Instagram, X, Reddit, Pinterest, Etsy, TikTok, Naver and Perplexity. API and MCP access come with every paid plan, no separate API product needed.
The limit to read carefully is the daily request cap. Starter at $68 a month allows 50 requests a day, Growth at $148 allows 100, Scale at $308 allows 200 and Agency at $628 allows 400, shared across the web interface, MCP and API. Fifty requests a day suits research and chokes automation, so check your call pattern before building. Volume data is Google Ads-based, which inflates some niches.
What we like- 16 platforms including Etsy, Instagram and Perplexity
- API and MCP on every paid plan
Watch out for- Metered in requests per day, not keywords
- Volume figures are Google Ads-based
Starting price$84/year (Bronze, 100,000 credits)
Free planFree API key (credits required for data calls)
Keywords Everywhere is the budget option for plain keyword metrics, and its pricing is refreshingly legible. One credit buys the volume, CPC, competition and 12-month trend for one keyword, up to 100 keywords per request. The API key itself is free and works on every plan including the $84-a-year Bronze tier with 100,000 credits. Higher tiers drop the per-keyword rate further.
What you give up is sophistication. There are no question, clustering or intent endpoints, billing is annual with no monthly option, and related-keyword and domain-keyword endpoints cost two credits per result and need the Gold tier or above. For a small tool that needs volume and nothing clever, the $84 entry point is the cheapest real API access here.
What we like- One credit per keyword, no unit math
- Volume, CPC, competition and trend in one response
- Official MCP server
Watch out for- Annual billing only
- No question or clustering endpoints
#7
Moz API
Best for: teams that need Domain Authority in their own tools
Visit moz.com
Starting price$20/month (Starter API, 3,000 rows)
Free planYes (50 rows per month)
Moz has run an API longer than most competitors, and its advantage is a metric the whole industry already speaks. Domain Authority and Page Authority appear in pitch decks, prospecting sheets and client reports everywhere, so piping them into your own tools removes a translation step. The API covers links, keywords, rank tracking and site crawls, with a free tier of 50 rows a month.
Pricing runs on rows, where one row is roughly one object or field in a response. Starter plans run $20 to $75 a month for 3,000 to 15,000 rows, Growth starts at $125 for 50,000 rows, and higher tiers climb into the thousands for millions of rows. Keyword data is thinner than Semrush or SE Ranking, and the link index misses things bigger crawlers catch.
What we like- DA and PA are understood by every client and stakeholder
- Long-running, stable API
- Keyword, link, rank and crawl endpoints
Watch out for- Link index smaller than Ahrefs or Semrush
- Row-based pricing takes learning
#8
Serpstat API
Best for: agencies piping Serpstat data into their own reports
Visit serpstat.com
Starting price$100/month (Team plan, API included)
Free planFree trial (7 days)
Serpstat bundles its API with the platform subscription rather than selling it separately, which keeps the math simple. The Individual plan at $50 a month has no API access, Team at $100 adds it with a 1-request-per-second limit, Team x2 at $169 raises the allowance to 400,000 API credits a month, and Agency at $410 doubles that with 10 requests per second. The available APIs cover search analytics, backlinks, rank tracking and site audit, so one integration can feed several report types.
The trade-off is that this is a suite API, not a standalone data product. You cannot buy API access without the platform, and the Individual tier is excluded entirely.
What we like- Search, backlink, rank tracking and site audit APIs in one subscription
- 400,000 API credits on Team x2
Watch out for- API starts on the Team tier, not Individual
- Enterprise volumes need a sales conversation
#9
Mangools API
Best for: small teams that want KWFinder data in internal dashboards
Visit mangools.com
Starting price$129/month (Agency plan, $89.90 billed annually)
Free planFree trial (10 days)
Mangools is best known for KWFinder, the friendliest keyword research interface in its price class, and its API extends that data to your own dashboards and scripts. The catch is placement: API access is only available on the Agency plan, which runs $129 a month or $89.90 a month billed annually, while Basic at $49 and Premium at $69 are excluded. That makes the API a meaningful step up from the plans most solo users buy.
What you get for the jump is straightforward keyword data with the same difficulty scoring that makes KWFinder popular, and the full five-tool suite, SERPWatcher, SERPChecker, LinkMiner and SiteProfiler, comes along. Limits and the backlink index are smaller than the enterprise providers, and there is no pay-as-you-go option.
What we like- Clean, simple responses that are easy to parse
- Keyword difficulty scores beginners understand
Watch out for- API access is gated behind the top tier
- Limits are modest next to enterprise APIs
Starting price$50/month (25,000 credits)
Free planFree trial
ValueSERP positions itself as the value play in SERP data, and the numbers back that up. Plans start at $50 a month for 25,000 credits ($1.60 per 1,000), rise to $240 for 200,000 ($1.20 per 1,000) and $1,000 for a million ($1.00 per 1,000), with annual billing shaving 10 percent. Requests run in real time or as scheduled batches of up to 15,000, with results delivered to S3, Google Cloud Storage or Azure.
The API renders pages in a full browser and parses result layouts without manual rules, and location and device targeting are supported. Coverage centers on Google, so teams needing Baidu, Naver or broad multi-engine support will look elsewhere. It comes from Traject Data, a smaller vendor, so documentation and community answers are thinner.
What we like- Among the lowest per-search rates available
- Batch scheduling with S3 delivery
- No card required to start
Watch out for- Google-focused engine coverage
- Smaller brand with less community history than SerpApi or DataForSEO
How we chose
We started from the keyword APIs that working SEO teams actually build on, then verified each against its pricing page, API docs and recent reviews on G2, Capterra and Reddit. Every product here offers a real, documented API for keyword or SERP data today. We excluded scraping libraries, unofficial wrappers and rank-only APIs. Prices were checked in October 2026 and will move, so confirm on the vendor page before budgeting.
What to check before you commit to a keyword API
Start with the unit of billing, because every vendor meters differently and the headline price rarely tells the story. DataForSEO bills per task and result, Ahrefs per integration unit with a 50-unit floor per request, Moz per row, SerpApi per search, Keyword Tool per request per day and Keywords Everywhere per keyword. Model your call pattern against each model before comparing prices, or the cheapest sticker becomes the most expensive bill.
Next, check data freshness and coverage for your markets. Ask how often keyword volumes update, how many countries and languages are covered, and whether the API returns the fields you actually need, search intent, SERP features, historical trends, or just volume and difficulty. A keyword API without the fields your product displays is a second integration waiting to happen.
Finally, look at the contract shape. Pay-as-you-go balances that never expire suit spiky research workloads, while monthly credit pools suit steady pipelines, but unused monthly credits usually vanish at renewal. Check rate limits too, since a 1-request-per-second cap turns a weekend backfill into a week-long job, and confirm the terms allow your use case.
Subscription plans vs pay-as-you-go
The keyword API market splits into two billing philosophies, and picking the wrong one is the most common way teams overpay. Subscription APIs, Ahrefs, Semrush, Serpstat, Mangools and Moz, bundle data access with a platform and reset your allowance monthly. They suit steady, predictable usage and punish spiky workloads, since quiet months still cost the full fee.
Pay-as-you-go providers, DataForSEO, SerpApi, ValueSERP and Keywords Everywhere, charge only for what you pull. DataForSEO and Keywords Everywhere even let balances or credits sit for a year or indefinitely, which fits research sprints, one-off audits and products with uneven demand. Per-unit rates can run higher than a subscription's effective rate at steady high volume, and prepaid balances tie up cash. If monthly usage swings more than 3x, pay-as-you-go usually wins; if it is flat, compare the subscription's effective per-unit cost honestly.
Frequently asked questions
Do I need a developer to use a keyword research API?
Yes, for nearly every API on this list. These are HTTP endpoints that return JSON, not dashboards, so someone needs to write the code that sends requests, handles errors and stores results. SerpApi's playground and vendor MCP servers lower the bar, but production use still needs technical ownership.
How much does it cost to pull keyword data at scale?
It depends on the billing model and your call pattern. As rough orientation, DataForSEO's keyword endpoints start near a tenth of a cent per keyword lookup, Keywords Everywhere runs under a tenth of a cent per keyword at its cheapest tier, and SerpApi starts at 2.5 cents per search on its entry plan. Suite APIs bundle richer data at higher per-unit cost. Always model your own volume first.
Can I use these APIs inside AI tools like Claude or ChatGPT?
Several vendors now ship MCP servers, including Ahrefs, DataForSEO, Keywords Everywhere and Keyword Tool. Usage still draws from your API allowance, so set spending limits before connecting an agent to a paid API.
Is scraping Google myself a real alternative?
Technically yes, practically rarely. Google's anti-bot systems mean you need proxy rotation, CAPTCHA solving and constant parser maintenance, and the legal position of scraping at scale is uncomfortable for most businesses. Every API here exists to absorb that cost. Self-scraping only pencils out where vendor pricing breaks, which for most teams is never.
Which API has the largest keyword database?
Among the suites, Semrush claims the largest at around 26 billion keywords, with Ahrefs close behind. DataForSEO aggregates multiple sources rather than maintaining one proprietary keyword index. For autocomplete-style discovery rather than database size, Keyword Tool's 16-platform coverage is the broader net. Bigger is not always better, though; match the database to the markets and languages you actually serve.
Sources we checked (14)
- https://dataforseo.com/pricing
- https://ahrefs.com/pricing
- https://www.semrush.com/api-documentation/api-units-pricing/
- https://serpapi.com/pricing
- https://keywordseverywhere.com/api-documentation.html
- https://keywordseverywhere.com/credits.html
- https://serpstat.com/prices/
- https://valueserp.com/pricing
- https://keywordtool.io/pro
- https://tryroki.com/blog/ahrefs-api-pricing-plans-limits-cost-guide
- https://ryandoser.com/semrush-api-pricing/
- https://scrapegraphai.com/blog/serpapi-pricing
- https://answersocrates.com/blog/best-keyword-research-apis/
- https://growthmethod.com/moz-data-mcp-server/
Is your product missing or out of date?
We review this list regularly. Vendors can request a listing, send updated pricing or ask about featured placement.
Shihab Mia · Founder, Rankite
Shihab has spent more than a decade helping SaaS and e-commerce brands grow through search. He writes Rankite's software buying guides from pricing pages, documentation and public user reviews. More about Shihab.