LanguageTool

Open-source grammar, style, and spell checking REST API supporting 25+ languages with AI-powered error detection, style suggestions, and text improvements. Used by 100+ companies to enhance software with proofreading capabilities via a simple HTTP API returning JSON responses. Hosted on GDPR-compliant servers in Germany with no text storage.

1 APIs 0 Features

GrammarSpell CheckStyleProofreadingNLPNatural Language ProcessingWritingOpen Source

APIs

LanguageTool Proofreading API

HTTP REST API for grammar, style, and spell checking across 30+ languages. Accepts POST requests with text and language parameters, returning JSON with detected errors, suggesti...

Pricing Plans

Plans

6 plans

PLANS

Rate Limits

0 limits

RATE LIMITS

FinOps

Finops

FINOPS

Example Payloads

Check Markup Request

2 fields

EXAMPLE

Check Text Request

3 fields

EXAMPLE

Check Text Response

3 fields

EXAMPLE

Words Add Request

3 fields

EXAMPLE

Resources

Sources

aid: languagetools
name: LanguageTool
description: Open-source grammar, style, and spell checking REST API supporting 25+ languages with AI-powered error detection,
  style suggestions, and text improvements. Used by 100+ companies to enhance software with proofreading capabilities via
  a simple HTTP API returning JSON responses. Hosted on GDPR-compliant servers in Germany with no text storage.
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
url: https://raw.githubusercontent.com/api-evangelist/languagetools/refs/heads/main/apis.yml
created: '2026-06-13'
modified: '2026-06-13'
specificationVersion: '0.19'
type: Index
tags:
- Grammar
- Spell Check
- Style
- Proofreading
- NLP
- Natural Language Processing
- Writing
- Open Source
apis:
- aid: languagetools:languagetool-api
  name: LanguageTool Proofreading API
  description: HTTP REST API for grammar, style, and spell checking across 30+ languages. Accepts POST requests with text
    and language parameters, returning JSON with detected errors, suggestions, and rule matches. Supports up to 60,000 characters
    per request with optional API key authentication for premium tiers.
  image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
  humanURL: https://languagetool.org/http-api/
  baseURL: https://api.languagetool.org/v2
  tags:
  - Grammar
  - Spell Check
  - Proofreading
  - Style
  - NLP
  properties:
  - type: Documentation
    url: https://languagetool.org/http-api/
  - type: OpenAPI
    url: https://raw.githubusercontent.com/api-evangelist/languagetools/main/openapi/openapi.json
common:
- type: Website
  url: https://languagetool.org
- type: Documentation
  url: https://languagetool.org/http-api/
- type: GitHubOrg
  url: https://github.com/languagetool-org
- type: LinkedIn
  url: https://www.linkedin.com/company/languagetool
- type: Blog
  url: https://languagetool.org/insights/
- type: Pricing
  url: https://languagetool.org/proofreading-api
- type: X
  url: https://x.com/languagetoolorg
- type: Plans
  url: https://raw.githubusercontent.com/api-evangelist/languagetools/refs/heads/main/plans/plans.yml
- type: RateLimits
  url: https://raw.githubusercontent.com/api-evangelist/languagetools/refs/heads/main/rate-limits/rate-limits.yml
- type: FinOps
  url: https://raw.githubusercontent.com/api-evangelist/languagetools/refs/heads/main/finops/finops.yml
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com