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API · /grammar-api

Grammar API

healthy 4,647 Subscribers

Catch spelling mistakes in six languages — English, German, Spanish, French, Portuguese and Dutch — and get English style and grammar suggestions in one call. Spelling errors come with their position in the text and a ranked list of corrections; style suggestions flag repeated words, weasel words, passive voice, wordiness, clichés and more. A combined check returns spelling and style together (sorted by position), a spelling-only endpoint covers all six languages, a single-word endpoint returns corrections for one word, and a languages endpoint lists what is supported. Every endpoint takes text via the query string or the request body and returns lean JSON. Pure server-side computation (Hunspell dictionaries + write-good, no third-party upstream, no LLM cost), so responses are instant and always available. Ideal for editors and CMSs, form and comment validation, chat and email tools, and writing assistants.

#grammar #spell-check #proofreading #spelling #writing #text #dev-tools
api.oanor.com/grammar-api
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Machine-readable spec so AI agents can integrate this API.

/api/grammar-api/openapi.json
/api/grammar-api/llms.txt

Discovery: GET /api/index.json lists every API.

Grammar API — live data on the oanor API marketplace

API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
73 ms
Server probes · 24h
Subscribers
4,647
active
Total calls
76
last 7 days
status Full status page → · 12 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 28,000 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • 28,000 calls/month, 2 req/s
  • Spelling in 6 languages + English style suggestions
  • No credit card
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Basic

€6.60 /month

  • 320,000 calls / month
  • 6 requests / second
  • Hard cap (429 above quota, no overage)
  • 320,000 requests/month, 6 req/s
  • All endpoints, combined spell + style checking
  • Commercial use included
  • Email support
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Pro

€19.50 /month

  • 2,400,000 calls / month
  • 22 requests / second
  • Hard cap (429 above quota, no overage)
  • 2,400,000 requests/month, 22 req/s
  • High throughput for editors & writing tools
  • Priority email support
  • Commercial use allowed
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Mega

€48.00 /month

  • 13,000,000 calls / month
  • 75 requests / second
  • Hard cap (429 above quota, no overage)
  • 13,000,000 requests/month, 75 req/s
  • Highest throughput for production proofreading at scale
  • Priority support
  • Commercial use allowed
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Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Grammar API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Grammar API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Grammar API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does Grammar API cost?
Grammar API has a free tier with 100 calls / month. Paid plans start at €6.60 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is Grammar API GDPR-compliant?
All requests to Grammar API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.

Pick an endpoint from the list on the left to see its details and try it.

Code snippets

Sign up to get an API key, then call any path under your slug.

curl https://api.oanor.com/grammar-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/grammar-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/grammar-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);
import requests
r = requests.get(
    "https://api.oanor.com/grammar-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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