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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
Get an API key Try in playground → Contact provider

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.

API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
80 ms
Server probes · 24h
Subscribers
4,647
active
Total calls
28
last 7 days
status Full status page → · 28 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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Built by

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PremiumApi

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api.oanor.com/words-api

Stopwords API

Stopword lists and removal for 58 languages. Fetch the full stopword list for a language, see all supported languages with their word counts, check whether a single word is a stopword, or strip stopwords out of a block of text to get a clean keyword stream. Built on the open stopwords-iso dataset and served entirely in-memory, so responses are instant and the service is always available. Ideal for search indexing and relevance, NLP preprocessing and text mining, keyword extraction, tag generation and content tooling.

api.oanor.com/stopwords-api

Emoji API

A complete emoji database in one fast API. Search roughly 1,870 emojis by name, keyword, alias or tag, look up a single emoji by its alias (like rocket or :fire:) or by the emoji character itself, browse any of the nine Unicode categories, or get random emojis (optionally from a category). Every emoji comes with its name, category, aliases, search tags, Unicode code points and the version it was introduced in. Built on the open GitHub gemoji dataset and served entirely in-memory, so responses are instant and the service is always available. Ideal for chat and messaging apps, emoji pickers and search, social and content tools, games and fun widgets.

api.oanor.com/emoji-api

Regex API

Run regular expressions server-side without the ReDoS risk. Test whether a pattern matches, extract all matches with their positions and capture groups (numbered and named), replace with a substitution pattern, or split text — all with the familiar JavaScript regex flags (g, i, m, s, u, y). Every evaluation runs in an isolated sandbox with a hard timeout, so a catastrophic-backtracking pattern can never hang your service; you get a clear timeout error instead. Inputs accept GET query parameters or a JSON POST body. Pure local compute with no third-party upstream, so responses are instant and the service is always available. Ideal for no-code and automation platforms, data-cleaning pipelines, form and input validation, log parsing and content tooling.

api.oanor.com/regex-api

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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