Get started with Copyleaks’ Grammar Checker API to detect and correct over 30 types of writing issues across grammar, mechanics, sentence structure, and word choice. The API is available in two ways:
  1. Sync: Submit text via an HTTP request and receive the analysis in the response.
  2. Async: Use the Authenticity API to submit larger documents and receive results via webhook.
This guide focuses on the synchronous option. For asynchronous submissions, see the Authenticity API Guide.

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Get started

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Before you begin

Before you start, ensure you have the following:
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Installation

Choose your preferred method for making API calls.
# macOS
brew install curl

# Ubuntu/Debian
sudo apt-get install curl

# Windows - download from https://curl.se
HTTP needs no installation - call the API with any standard HTTP client, or import our Postman collection for a quicker start.
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Login

To perform a scan, we first need to generate an access token. For that, we will use the login endpoint. The API key can be found on the Copyleaks API Dashboard.Upon successful authentication, you will receive a token that must be attached to subsequent API calls via the Authorization: Bearer <TOKEN> header. This token remains valid for 48 hours.
POST https://id.copyleaks.com/v3/account/login/api

Headers
Content-Type: application/json

Body
{
    "email": "[email protected]",
    "key": "00000000-0000-0000-0000-000000000000"
}
Response
{
    "access_token": "<ACCESS_TOKEN>",
    ".issued": "2025-07-31T10:19:40.0690015Z",
    ".expires": "2025-08-02T10:19:40.0690016Z"
}
Save this token. It is valid for 48 hours and can be reused for subsequent API calls.
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Send request

Use the Writing Feedback Endpoint. Provide a unique scanId for each request.
For testing, set "sandbox": true in the request body. Sandbox mode is free and returns mock results.
POST https://api.copyleaks.com/v1/writing-feedback/my-scan-1/check

Headers
Authorization: Bearer <YOUR_AUTH_TOKEN>
Content-Type: application/json

Body
{
  "text": "Copyleaks is a online plagarism detector that helps schools, business and content creators to make sure thier work is orginal. It scans textes from internet and databasis to find similerities. The tool is fast, accurate and supports multipal languages. However, some times it gives false possitives, so users should double check results. Overall, its a usefull platform for mantaining content integrity.",
  "sandbox": true
}
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Interpreting the response

The Grammar Checker Response contains detailed feedback under the corrections and score properties. The score provides an overall quality metric and a breakdown by category, while corrections pinpoints the exact location and suggested changes for each issue.
Example Response Snippet
{
  "score": {
    "corrections": {
      "overallScore": 93,
      "grammarCorrectionsScore": 100
    },
    "readability": {
      "readabilityLevelText": "College Student"
    }
  },
  "corrections": {
    "text": {
      "chars": { "types": [18], "starts": [28], "lengths": [9], "operationTexts": ["stretches "] }
    }
  }
}

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Next steps

Full API Reference

Explore the complete documentation for the Grammar Checker response object.

Correction Types

See a detailed list of all supported correction types and languages.

Try it

Test the Copyleaks grammar checker with your own text and see suggestions in seconds.