Seonio SEO API: Keyword, SERP, Traffic, Ranking and Backlink Data as JSON

Updated 13 October 2026: 21 endpoints, current prices and plans.

The Seonio SEO API gives you keyword metrics, Google results, organic traffic, rankings, authority scores and backlinks as JSON. Send a POST request with your API key, and you get structured data back for your product, dashboard or script. Prices start at $0.001 per request, and a free account comes with a $1 testing balance.

Send your first request

Every endpoint is a POST with a JSON body and an X-API-Key header. Your API key is under Settings in your Seonio account.

curl -X POST https://seonio.com/api/v1/keywords/global \
  -H "Content-Type: application/json" \
  -H "X-API-Key: $SEONIO_API_KEY" \
  -d '{"keywords": ["keyword research"]}'

The response from a request in June 2026, shortened to two of its 12 months:

{
  "keywords": [
    {
      "text": "keyword research",
      "volume": 550000,
      "cpc": 37,
      "competition": 1,
      "monthly_trend": [
        {"month": "2026-05", "value": 450000},
        {"month": "2026-04", "value": 201000}
      ]
    }
  ]
}

Each endpoint has a documentation page with its request and response fields, examples and a playground where you can try it before you write code.

Choose an endpoint

Every path starts with https://seonio.com/api/v1/. All endpoints read data; none changes anything in your account. Endpoints that take a country cover up to 50 markets, including the United States, the United Kingdom, Germany, France, Spain, India, Brazil and Japan. If an endpoint doesn't support a country, it returns 422 and charges nothing.

Keywords

Endpoint	What it returns	Price
keywords/global	Search volume, cost per click, competition and a 12-month trend for up to 100 keywords	$0.001 per keyword
keywords/country	The same metrics plus difficulty and intent for up to 500 keywords in one country	$0.010 per request plus $0.001 per started 10 keywords
keywords/suggestions	Up to 100 related keyword ideas for a seed keyword, with metrics	$0.020
keywords/clustering	Topic clusters for a seed keyword, grouped by shared search results	$0.250
keywords/difficulty	How hard a keyword is to rank for in a country	$0.005
keywords/intent	Search intent of up to 100 keywords	$0.001 per keyword
keywords/demographics	Age and gender of the people searching	$0.010

Search results and pages

Endpoint	What it returns	Price
serp/country	Google's results page for a keyword in a country	$0.001
serp/scraper	The results page plus the content of 1 to 10 top results as Markdown	$0.001 plus $0.002 per page fetched
scraper	The content of one known URL as clean Markdown or raw HTML	$0.002
audit/page-checker	On-page SEO findings for a URL, with a score	$0.005

Domains and URLs

Endpoint	What it returns	Price
website/traffic	Monthly organic traffic estimates for a domain	$0.010
website/ranking	The keywords and pages a domain ranks for, its top countries and position changes	$0.020
url/keywords	The keywords one page ranks for	$0.020
website/stats	Authority scores, spam score and linking domains for a domain	$0.002
url/stats	The same metrics for a full URL	$0.002
website/competitors	Domains that compete for the same organic keywords	$0.010
website/category	Which category a domain belongs to	$0.001
website/similar	Other sites in the same category	$0.001

Backlinks

Endpoint	What it returns	Price
backlink/table	The links pointing to a domain or a full URL	$0.020
backlink/history	How a domain's backlink profile changed over time	$0.020

The same data is available to AI assistants through Seonio MCP at the same prices.

Know what you pay

The API, MCP and the Seonio website share one balance and the same prices. Each price is in dollars, so you can see the cost of a request before you send it.

• Try it for free. A free account gets a $1 testing balance, once per person, with no card or subscription.
• Use a plan for regular work. Starter ($15 a month), Pro ($30) and Business ($60) include $15, $37.50 and $90 of usage every month. Included usage doesn't carry over to the next month. On any plan, Extra Usage packs add balance that's valid for one year.
• Know the order. Seonio spends your testing balance first, then your included monthly usage, then Extra Usage, starting with the pack that expires first.
• No overage bills. If your balance runs out, requests return 402 until your plan renews or you add an Extra Usage pack. On a free account, start a plan to continue.

The pricing page always has the current plans and prices.

Handle errors without paying for them

A completed lookup is charged, even when it finds no data, because an empty answer is real information. Requests that fail or can't be answered aren't charged.

Status	What it means	Charged?
200	The lookup completed, even if the result is empty	Yes
401	Missing or unknown API key	No
402	Not enough balance	No
403	The account isn't verified yet, or it's locked	No
422	Invalid request, such as a wrong field, a domain that doesn't exist or an unsupported country	No
429	Too many requests per second	No
503	The lookup failed on our side; try again after the seconds in the Retry-After header	No

Requests per second depend on your plan: 5 on a free account, 10 on Starter, 15 on Pro and 20 on Business. If you get a 429, wait for the seconds in the Retry-After header and send the request again.

What you can build

• Keyword features in your product: volumes, difficulty and intent next to your users' own data.
• Competitor dashboards: traffic trends, ranking keywords and competing domains for a list of sites.
• Link prospecting: authority scores and backlinks to qualify sites before outreach.
• Content briefs: today's top results for a keyword as Markdown, ready for an editor or an AI model.
• Client reports: monthly traffic, rankings and backlinks for each client, pulled by a script instead of by hand.

Get started

Create a free account, copy your API key from Settings and send your first request. The API overview lists every endpoint with its documentation and playground.