Best Keyword Research Tool API: 6 Options Compared

How we chose

The starting point was price transparency: an API belongs on this list only if its per-request cost can be worked out from published pricing. Every pick was then checked for what a keyword request actually returns — search volume, keyword difficulty or autocomplete ideas — and for the limits that catch you out, such as rows per request and requests per day. Prices and limits below are based on published pricing and documentation, checked on 13 November 2026. No hands-on testing was done.

1. DataForSEO: best for bulk keyword data at the lowest per-keyword cost

DataForSEO sells keyword data by the task, not by the month. Its Google Ads API costs $0.06 per task on the standard queue and $0.09 per task live, with each task covering up to 1,000 keywords. The Bing Ads API costs the same. A separate Labs API returns keyword ideas at $0.012 per task plus $0.00012 per item. There is no monthly fee, and the minimum deposit is $50, which buys a lot of keyword data at these rates.

The trade-off is that you get raw data and nothing else. There is no dashboard, no keyword list builder and no reporting — you build the interface yourself or plug the API into a tool you already use. That makes DataForSEO the right pick for developers, agencies that run keyword research at volume, and anyone who already has a workflow and just needs cheap data. If you want a ready-made interface, one of the suites below fits better. The $50 deposit also means it is not the best choice for a one-off lookup of a handful of keywords.

2. KeywordTool.io: best for long-tail autocomplete keyword ideas

KeywordTool.io works differently from the other picks here. Instead of returning search volume for keywords you already know, it pulls autocomplete suggestions from Google, YouTube, Amazon, Bing and 13 other platforms, which is how you find long-tail phrases people actually type. The API is included in every paid plan, and bulk search volume lookups handle up to 1,000 keywords per request.

The Starter plan costs $88 a month, or $68 a month billed annually, and allows 50,000 keywords a day with 50 API requests a day. Higher plans raise the daily keyword allowance to 400,000 on the Agency plan, which costs $788 a month, or $628 a month billed annually. The free version shows keyword ideas but no search volume, so you can see whether the autocomplete data is useful before you pay. There is no free trial, but there is a 30-day money-back guarantee.

Skip this one if you need keyword difficulty, backlink data or rank tracking — it does none of those. It is a keyword idea engine with an API, not a full SEO suite.

3. Ahrefs: best for keyword data inside a full SEO suite

Ahrefs gives you API access on its Lite plan and above, starting at $129 a month with an annual commitment. The $29-a-month Starter plan does not include API access, so that is a dead end for API buyers. API units are 200,000 a month on Lite, 800,000 on Standard, 2 million on Advanced and 4 million on Enterprise, with a maximum of 100 rows per request on Lite rising to unlimited on Enterprise.

The keyword data is strong — Ahrefs' keyword database and difficulty scores are widely used — but you are paying for a full SEO suite: Site Explorer, Site Audit, rank tracking and content tools all come with it. That is good value if your team already uses Ahrefs, and poor value if you only need keyword volume. The API also uses MCP access, which suits teams wiring AI assistants into their workflow. If your keyword needs are small, the $129 entry price is hard to justify against the pay-as-you-go options above.

4. Semrush: best for API data inside an enterprise SEO platform

Semrush has changed how it sells API access. Its pricing page now lists four plans — SEO at $139.95 a month, Starter at $199, Pro+ at $299 and Advanced at a custom price — and "Advanced API data integration" is listed only under the Advanced plan. The $549 figure for Advanced that still appears in older articles is out of date; the plan is now priced on request.

API units are bought separately in packages of 2 million, 5 million, 10 million or 20 million units, with no public per-unit price. A free Semrush account exists, but it does not include API access. That puts Semrush out of reach for most small teams: you need a sales conversation before you know the cost. The pick earns its place here because large teams already on Semrush get a deep keyword database, competitive data and reporting in one contract. If you are not already a Semrush customer, start with DataForSEO or Moz API and revisit Semrush when your volume justifies an enterprise conversation.

5. Moz API: best for a simple standalone API with a free tier

Moz sells its API separately from Moz Pro, which keeps the pricing simple. The free tier gives you 50 rows a month with one request every 10 seconds, though it needs a credit card to activate. Paid plans start at $20 a month for 3,000 rows, or $75 a month for 15,000 rows, with larger plans at $125, $250 and $500 a month for 50,000, 120,000 and 500,000 rows. The Advanced plan costs $2,000 a month for 4 million rows, and Enterprise is custom.

The data covers the metrics most people need from a keyword API: search volume, difficulty, organic click-through rate and SERP features, plus domain authority for the ranking URLs. The row-based pricing is easy to budget, and the free tier is enough to test an integration properly. The weakness is depth: Moz's keyword database is smaller than Ahrefs' or Semrush's, and the API does not include the full Moz Pro toolset. For a small tool, a side project or a first API integration, that trade-off is usually worth it.

6. SE Ranking: best for a standalone API with an annual credit pool

SE Ranking sells its Data API as a standalone product from $179 a month billed annually, which buys 1 million credits a year. A Wallet option lets you buy 250,000 credits for $50, and those credits never expire. As an add-on to the SE Ranking platform it costs $45 a month billed annually, and the Core platform plan at $129 a month ($103.20 billed annually) includes 25,000 API credits plus MCP access.

That flexibility is the appeal: you can buy credits as you need them, commit to an annual pool, or add the API to a platform subscription you already have. The API covers keyword data, backlinks, rank tracking and site audits, so it is broader than a keyword-only feed. The 14-day free trial lets you test it without a card. The entry price is higher than Moz or DataForSEO, so it suits teams with steady volume rather than occasional lookups.

Worked example: what 100,000 keywords a month costs

Take a team that checks search volume for 100,000 keywords a month:

• DataForSEO: 100 tasks at $0.06 = $6 a month on the standard queue, or $9 live. Add $13.20 if you also pull 100,000 keyword ideas through the Labs API.
• Moz API: 100,000 rows needs the $250-a-month plan (120,000 rows). $250 a month.
• KeywordTool.io: the Starter plan at $88 a month covers 50,000 keywords a day, so 100,000 a month fits easily. $88 a month ($68 billed annually).
• Ahrefs: Lite at $129 a month gives 200,000 API units. $129 a month.
• SE Ranking: the Wallet option, $50 for 250,000 credits, covers several months at this volume. Roughly $20 a month averaged out.
• Semrush: custom pricing — no number to quote.

The gap between the cheapest and the suite options is roughly twenty-fold, which is why the first question is always how much data you actually need.

How to choose

Who should not buy which

• Do not buy Semrush if you need a price today — the Advanced plan is custom-priced and needs a sales call.
• Do not buy Ahrefs if you only need keyword volume. The $129 entry price buys a suite you may never open.
• Do not buy KeywordTool.io if you need keyword difficulty or backlink data. It returns ideas and volume, not authority metrics.
• Do not buy DataForSEO if you want a dashboard. It is raw data with no interface, and the $50 minimum deposit is wasted on a one-off lookup.

How to choose an API without overpaying

Start with the free tier or the cheapest pay-as-you-go option and measure your real usage for a month before committing to a subscription. Most teams overestimate their keyword volume — a keyword research tool under $50 a month is often enough for a small site, and the best rank tracking software covers the monitoring side that APIs do not. If you also need backlink data, compare the best backlink checking tool before buying a suite for its API alone, and check Keyword.com alternatives if rank tracking is the main job. For the wider picture, Adziq's SEO services cover keyword research as part of a managed campaign.

Common questions

Sources

• Keyword Data API (DataForSEO)
• KeywordTool.io Pro plans
• Ahrefs pricing
• Semrush pricing
• Moz API pricing
• SE Ranking Data API pricing

Adziq sells marketing services and does not accept payment for placement in its articles. See our editorial policy.