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Introducing DeepL API for Write

DeepL API for Write is now generally available via the v2 API endpoint for customers with a DeepL API Pro subscription.

The supported scope of DeepL API for Write functionality is covered in this documentation page. Please note that the existing provisions applying to customers' DeepL API Pro subscription also apply to DeepL API for Write with the following additions to the Service Specification.

An FAQ is included at the bottom of this page.

DeepL API for Write overview

DeepL API for Write is accessible through an HTTP interface and currently consists of a single endpoint for text improvement, /write/rephrase, which is described below. The endpoint:

  • Accepts both form-encoded (Content-Type: application/x-www-form-urlencoded) and JSON-encoded (Content-Type: application/json) request bodies

  • Returns JSON-encoded responses

Client library support will be added in the near future.

The text improvement feature is currently only available to DeepL API Pro customers and is not yet available in DeepL API Free.

For more detail about request body parameters, see the Request body descriptions section further down the page.

The total request body size for text improvement requests must not exceed 10 KiB (10 · 1024 bytes). Please split up your text into multiple calls if it exceeds this limit.

Example cURL request and response

These examples are for demonstration purposes only. In your code, the authentication key should not be hard-coded but instead fetched from a configuration file or environment variable.

Example cURL request
curl -X POST 'https://api.deepl.com/v2/write/rephrase' \
--header 'Authorization: DeepL-Auth-Key [yourAuthKey]' \
--header 'Content-Type: application/json' \
--data '{
  "text": [
    "I could relly use sum help with edits on thiss text !"
  ],
  "target_lang": "en-US"
}'
Example response
{
  "improvements": [
    {
      "text": "I could really use some help with editing this text!",
      "target_language": "en-US",
      "detected_source_language": "en"
    }
  ]
}

Request body descriptions

Body Parameter
Description

text (required)

Text to be improved. Only UTF-8-encoded plain text is supported. Improvements are returned in the same order as they are requested. Each of the parameter values may contain multiple sentences.

All texts must be in the same language.

Type: array[string]

target_lang (optional)

The language of the improved text. A list of supported languages have not yet been added to the /languages endpoint. At the time of the beta, the following languages are supported:

  • de (German)

  • en-GB (British English)

  • en-US (American English)

  • es (Spanish)

  • fr (French)

  • it (Italian)

  • pt-BR (Brazilian Portuguese)

  • pt-PT (Portuguese)

The language of the source texts sent in the text parameter must match the target language (translating and improving text simultaneously is not yet supported).

Note that it is possible to convert text from one variant to another within a language. For example, if American English is sent in an API request with target_lang set to EN-GB, the submitted text will be improved and also converted to British English.

Type: string

writing_style (optional)

Changes the writing style of your improvements.

Supported values:

  • simple

  • business

  • academic

  • casual

  • default

  • prefer_simple

  • prefer_business

  • prefer_academic

  • prefer_casual

Using the defaultvalue behaves the same as not sending a writing_style.

Currently supported for the following target languages:

  • de

  • en-GB

  • en-US

Styles prefixed with prefer_ will fall back to the default style when used with a language that does not support styles (this is recommended for cases where no target_lang is set), the non-prefixed writing styles (except default) will return a HTTP 400 error in that case.

It’s not possible to include both writing_style and tone in a request; only one or the other can be included. Type: enum

tone (optional)

Changes the tone of your improvements.

Supported values:

  • enthusiastic

  • friendly

  • confident

  • diplomatic

  • default

  • prefer_enthusiastic

  • prefer_friendly

  • prefer_confident

  • prefer_diplomatic

Using the defaultvalue behaves the same as not sending a tone.

Currently supported for the following target languages:

  • de

  • en-GB

  • en-US

Tones prefixed with prefer_ will fall back to the default tone when used with a language that does not support tones (this is recommended for cases where no target_lang is set), the non-prefixed tones (except default) will return a HTTP 400 error in that case.

It’s not possible to include both writing_style and tone in a request; only one or the other can be included. Type: enum

Response body descriptions

The /write/rephrase endpoint returns a JSON object with Improvements under the improvements key, which contains an array of text, target_language, and detected_source_language objects. Improvements are returned in the same order as they are requested.

Body parameter
Description

text

The improved text Type: string

target_language

The target language specified by the user. Type: string

detected_source_language

The detected source language of the text provided in the request. Type: string

Frequently asked questions

Does Cost Control factor in Write API usage?

Yes. If you set a Cost Control limit, it will be enforced against a sum of Translate API + Write API characters. At this time, it is not possible to set separate Translate API and Write API cost control limits.

Does the /usage endpoint response include Write API characters?

Yes, the character_count field in the /usage endpoint response returns a sum of Translate API + Write API characters. You can learn more about the /usage endpoint here.

Do I access the DeepL Write API with the same API keys from my Pro API subscription?

Yes! The Write API is accessed using the same API keys in the API Keys tab that you use to access all other DeepL API endpoints.

Can I see DeepL Write API usage in my reporting?

We've added a new column to the API key-level usage report that breaks out text improvement characters separately. The character counts in the Usage tab of your API account are a sum of both Translate and Write characters; these are not yet broken out separately.

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