SEO Data Bench/Benchmarks/keyword-data-coverage
Keyword volume coverage: which APIs report the long tail at all
Fifty US-English buyer keywords sent to DataForSEO, Serpstat, SE Ranking and Google Ads Keyword Planner in one call each. How many came back with a number, how the numbers compare with Google's own, and how each provider signals 'no data'.
Written for people asking: How do I get keyword volumes without several monthly SEO subscriptions?Which keyword research API has the best coverage of long-tail keywords?Is DataForSEO search volume the same as Google Keyword Planner?
On cohort v1 (50 keywords, US English, 15 September 2026) DataForSEO returned a volume for 31 of 50 keywords and matched Google Ads Keyword Planner exactly on every one of the 30 it shares, which is expected because its search_volume endpoint is Google Ads data resold. SE Ranking returned a volume for 25 of 50 and was within a factor of two of Google on 23 of 24, but reported 'serp api' at 3,100 against Google's 12,100 and had no value for several 10-to-30-a-month terms Google reports. Serpstat returned only 23 of the 50 keywords at all, ran about 20% higher than Google on the ones it had, and reported '1' for two terms Google shows no data for. None of the four reported a zero; the long tail comes back as null or absent, and the difference between those two is the coverage signal.
Why coverage, not accuracy
There is no ground truth for search volume. Google’s own Keyword Planner rounds to buckets, merges close variants and is designed for advertisers, not for measuring demand. So this page does not rank providers on accuracy. It measures the two things an API buyer can actually observe: whether a keyword comes back with a number at all, and how far that number sits from Google’s, which is the figure everyone else is ultimately modelling.
The cohort is deliberately half long tail. Twenty of the 50 keywords have no reported Google volume. A provider that only covers head terms looks fine on a list of head terms and useless on an agent’s real queries.
Results
| Provider | Keywords returned | With a volume | Within 2× of Google Ads | Median log10 ratio vs Google | Latency (one bulk call) | Cost for 50 keywords |
|---|---|---|---|---|---|---|
| DataForSEO | 50 | 31 | 30/30 | 0 | 4205 ms | $0.090 |
| Google Ads (Keyword Planner) | 49 | 30 | — | — | 2097 ms | $0.0000 |
| SE Ranking | 50 | 25 | 23/24 | 0 | 4032 ms | $0.089 |
| Serpstat | 23 | 23 | 18/21 | 0.09 | 4066 ms | $0.025 |
Reading the table:
- DataForSEO is Google Ads. Its
keywords_data/google_ads/search_volumeendpoint returned a value for 31 keywords and matched Keyword Planner to the digit on all 30 they share. The 31st is “backlink api”, which Google merged into “backlinks api” as a close variant and dropped from its own response. If you already have a Google Ads account, the same numbers are free through the Keyword Planner API; DataForSEO’s value is not having to run an Ads account and the ability to send 1,000 keywords per call for $0.09. - SE Ranking has its own model. It agrees with Google within a factor of two on 23 of the 24 keywords both report, but the exception is the biggest term in the cohort: “serp api” at 3,100 against Google’s 12,100. It also returned no value for six terms Google puts at 10 to 30 searches a month, so its long-tail coverage is thinner than DataForSEO’s even though it returned all 50 rows.
- Serpstat returns only what is in its database. Twenty-seven of the 50 keywords were absent from the response entirely. On the 21 it shares with Google it ran about 20% higher on median. Two of its values are a bare “1” for terms Google reports as no data, which reads as a floor rather than a measurement.
- Nobody reports zero. All four providers signal no demand as null or by omitting the row, never as 0. A pipeline that treats null as zero will silently mark 40% of this cohort as dead keywords.
Every keyword, every provider
“null” means the provider returned the keyword without a volume. “absent” means the provider did not return the keyword at all. Google Ads shows “absent” once, for the close-variant merge described above.
| Keyword | Google Ads | DataForSEO | SE Ranking | Serpstat |
|---|---|---|---|---|
| data enrichment api | 50 | 50 | 70 | 110 |
| contact enrichment api | 40 | 40 | 30 | 50 |
| company enrichment api | 30 | 30 | 40 | 50 |
| email enrichment api | 20 | 20 | 30 | 30 |
| b2b enrichment api | — | — | — | absent |
| waterfall enrichment | 170 | 170 | 140 | absent |
| waterfall enrichment api | 10 | 10 | — | absent |
| pay as you go enrichment | — | — | — | absent |
| pay per call api | — | — | — | 1 |
| enrichment api for ai agents | — | — | — | absent |
| mcp enrichment | — | — | — | absent |
| clay alternatives | 480 | 480 | 480 | 480 |
| apollo alternatives | 390 | 390 | 390 | absent |
| people data labs alternatives | 30 | 30 | — | absent |
| openrouter for tools | 10 | 10 | — | absent |
| api marketplace for ai agents | — | — | — | absent |
| ai agent tools api | — | — | — | absent |
| seo api | 390 | 390 | 480 | 480 |
| serp api | 12,100 | 12,100 | 3,100 | 12,100 |
| keyword data api | 30 | 30 | 40 | 50 |
| backlinks api | 110 | 110 | 140 | 140 |
| meta ad library api | 320 | 320 | — | 210 |
| google ads transparency api | 30 | 30 | 30 | absent |
| competitor ads api | — | — | — | absent |
| ad library api | 50 | 50 | 40 | 30 |
| social media scraping api | 30 | 30 | 30 | absent |
| enrichment api | 70 | 70 | 70 | 1 |
| best enrichment api | — | — | — | absent |
| best contact enrichment api | — | — | — | absent |
| best company enrichment api | — | — | — | absent |
| company data api | 40 | 40 | 50 | 70 |
| b2b data api | 30 | 30 | 30 | 30 |
| person enrichment api | 10 | 10 | — | absent |
| email finder api | 40 | 40 | 40 | 40 |
| email verification api | 210 | 210 | 210 | 260 |
| linkedin enrichment api | 10 | 10 | — | absent |
| company enrichment api pricing | — | — | — | absent |
| contact enrichment api pricing | — | — | — | absent |
| pay as you go data enrichment | — | — | — | absent |
| pay per call enrichment api | — | — | — | absent |
| clay api alternative | — | — | — | absent |
| clay alternatives for developers | — | — | — | absent |
| waterfall enrichment api pricing | — | — | — | absent |
| serpapi alternatives | 110 | 110 | 140 | 170 |
| dataforseo alternatives | 30 | 30 | 30 | 30 |
| seo data api | 140 | 140 | 140 | 170 |
| seo api pricing | — | — | — | absent |
| keyword research api | 90 | 90 | 90 | 140 |
| keyword search volume api | 30 | 30 | 40 | 70 |
| backlink api | absent | 110 | 140 | 210 |
Who each route fits
- You have a Google Ads account: call Keyword Planner directly. It is free, and it is the source the paid routes resell or model.
- You want Google’s numbers without an Ads account, in bulk: DataForSEO, $0.09 for up to 1,000 keywords per call, prepaid balance, no plan.
- You want a second opinion with difficulty and intent fields: SE Ranking, but check its long-tail coverage on your own vocabulary first.
- You already pay for Serpstat: use it for the head terms it has; do not rely on it to tell you a term has no demand.
What this run cannot tell you
One market, one day, one vocabulary. Coverage on non-English markets, on e-commerce or local vocabularies, or on Bing will differ. The comparison point is Google Ads, which is itself rounded and variant-merged, so “within 2×” is a loose bound, not a precision claim. A second dated run is scheduled; run-to-run stability will be reported once it exists.
Reproduce it
The cohort, runner and scorer are on the dataset page; the four raw keyword responses are under evidence.
Spotted an error or a changed price? Email corrections@seodatabench.com with the page URL and a source. Corrections are logged on the corrections page.