Translate text

API reference for translating text with the DeepL API.

The text-translation API currently consists of a single endpoint, translate, which is described below.

To learn more about context in DeepL API translations, we recommend this article.

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

We also provide a spec that is auto-generated from DeepL's OpenAPI file. You can find it here.

The total request body size for text translation requests must not exceed 128 KiB (128 · 1024 bytes). Please split up your text into multiple calls if it exceeds this limit.

The examples below use our API Pro endpoint https://api.deepl.com. If you're an API Free user, remember to update your requests to use https://api-free.deepl.com instead.

Example request: text translation (without glossary)
curl -X POST 'https://api.deepl.com/v2/translate' \
--header 'Authorization: DeepL-Auth-Key [yourAuthKey]' \
--header 'Content-Type: application/json' \
--data '{
  "text": [
    "Hello, world!"
  ],
  "target_lang": "DE"
}'
Example request: text translation (with glossary)
curl -X POST 'https://api.deepl.com/v2/translate' \
--header 'Authorization: DeepL-Auth-Key [yourAuthKey]' \
--header 'Content-Type: application/json' \
--data '{
  "text": [
    "Hello, world!"
  ],
  "target_lang": "DE",
  "source_lang": "EN",
  "glossary_id": "[yourGlossaryId]"
}'
Example response
{
  "translations": [
    {
      "detected_source_language": "EN",
      "text": "Hallo, Welt!"
    }
  ]
}

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

Note that we do not include examples for our client libraries in every single section of this reference, but our client libraries do support all use cases shown on this page.

Request Body Descriptions

Body parameterDescription

text (required)

Text to be translated. Only UTF-8-encoded plain text is supported. The parameter may be specified multiple times and translations are returned in the same order as they are requested. Each of the parameter values may contain multiple sentences. Up to 50 texts can be sent for translation in one request. Type: array[string]

source_lang (optional)

Language of the text to be translated. If omitted, the API will attempt to detect the language of the text and translate it. You can find supported source languages here. Type: string

target_lang (required)

The language into which the text should be translated. You can find supported target languages here. Type: string

context (optional)

The context parameter makes it possible to include additional context that can influence a translation but is not translated itself. This additional context can potentially improve translation quality when translating short, low-context source texts such as product names on an e-commerce website, article headlines on a news website, or UI elements.

For example:

  • When translating a product name, you might pass the product description as context.

  • When translating a news article headline, you might pass the first few sentences or a summary of the article as context.

For best results, we recommend sending a few complete sentences of context. There is no size limit for the contextparameter itself, but the request body size limit of 128 KiB still applies to all text translation requests.

If you send a request with multiple text parameters, the context parameter will be applied to each one.

The context parameter is an alpha feature and is not intended for production use at this time. Learn more about alpha features here.

While the feature is still labeled as "alpha", context will not be counted toward billing (i.e. there is no additional cost for sending context). This is subject to change if the "alpha" label is removed and the feature becomes generally available. If we decide to deprecate the contextparameter, requests that include it will not break; the context will simply be ignored.

We're eager to hear how the context parameter is working for you and how we can improve the feature! You can share your feedback by emailing api-feedback@deepl.com. Type: string

split_sentences (optional)

Sets whether the translation engine should first split the input into sentences. For text translations where tag_handling is not set to html, the default value is 1, meaning the engine splits on punctuation and on newlines.

For text translations where tag_handling=html, the default value is nonewlines, meaning the engine splits on punctuation only, ignoring newlines.

The use of nonewlines as the default value for text translations where tag_handling=html is new behavior that was implemented in November 2022, when HTML handling was moved out of beta.

Possible values are:

  • 0 - no splitting at all, whole input is treated as one sentence

  • 1 (default when tag_handling is not set to html) - splits on punctuation and on newlines

  • nonewlines (default when tag_handling=html) - splits on punctuation only, ignoring newlines

For applications that send one sentence per text parameter, we recommend setting split_sentences to 0, in order to prevent the engine from splitting the sentence unintentionally.

Please note that newlines will split sentences when split_sentences=1. We recommend cleaning files so they don't contain breaking sentences or setting the parameter split_sentences to nonewlines. Type: string

preserve_formatting (optional)

Sets whether the translation engine should respect the original formatting, even if it would usually correct some aspects.

The formatting aspects affected by this setting include:

  • Punctuation at the beginning and end of the sentence

  • Upper/lower case at the beginning of the sentence

Type: boolean

formality (optional)

Sets whether the translated text should lean towards formal or informal language. This feature currently only works for target languages DE (German), FR (French), IT (Italian), ES (Spanish), NL (Dutch), PL (Polish), PT-BR and PT-PT (Portuguese), JA (Japanese), and RU (Russian). Learn more about the plain/polite feature for Japanese here. Setting this parameter with a target language that does not support formality will fail, unless one of the prefer_... options are used. Possible options are:

  • default (default)

  • more - for a more formal language

  • less - for a more informal language

  • prefer_more - for a more formal language if available, otherwise fallback to default formality

  • prefer_less - for a more informal language if available, otherwise fallback to default formality

Type: string

glossary_id (optional)

Specify the glossary to use for the translation. Important: This requires the source_lang parameter to be set and the language pair of the glossary has to match the language pair of the request. Type: string

tag_handling (optional)

Sets which kind of tags should be handled. Options currently available:

Type: string

outline_detection (optional)

The automatic detection of the XML structure won't yield best results in all XML files. You can disable this automatic mechanism altogether by setting the outline_detection parameter to false and selecting the tags that should be considered structure tags. This will split sentences using the splitting_tags parameter.

In the example below, we achieve the same results as the automatic engine by disabling automatic detection with outline_detection=0 and setting the parameters manually to tag_handling=xml, split_sentences=nonewlines, and splitting_tags=par,title.

Example request:

<document>
  <meta>
    <title>A document's title</title>
  </meta>
  <content>
    <par>This is the first sentence. Followed by a second one.</par>
    <par>This is the third sentence.</par>
  </content>
</document>

Example response:

<document>
  <meta>
    <title>Der Titel eines Dokuments</title>
  </meta>
  <content>
    <par>Das ist der erste Satz. Gefolgt von einem zweiten.</par>
    <par>Dies ist der dritte Satz.</par>
  </content>
</document>

While this approach is slightly more complicated, it allows for greater control over the structure of the translation output. Type: boolean

non_splitting_tags (optional)

Comma-separated list of XML or HTML tags which never split sentences. Learn more. Type: array[string]

splitting_tags (optional)

Comma-separated list of XML or HTML tags which always cause splits. Learn more. Type: array[string]

ignore_tags (optional)

Comma-separated list of XML or HTML tags that indicate text not to be translated. Learn more. Type: array[string]

Multiple Sentences

The translation function will (by default) try to split the text into sentences before translating. Splitting normally works on punctuation marks (e.g. "." or ";"), though you should not assume that every period will be handled as a sentence separator. This means that you can send multiple sentences as a value of the text parameter. The translation function will separate the sentences and return the whole translated paragraph.

In some cases, the sentence splitting functionality may cause issues by splitting sentences where there is actually only one sentence. This is especially the case if you're using special/uncommon character sequences which contain punctuation. In this case, you can disable sentence splitting altogether by setting the parameter split_sentences to 0. Please note that this will cause overlong sentences to be cut off, as the DeepL API cannot translate overly long sentences. In this case, you should split the sentences manually before submitting them for translation.

The example below uses our API Pro endpoint https://api.deepl.com. If you're an API Free user, remember to update your requests to use https://api-free.deepl.com instead.

Example request: multiple sentences
curl -X POST 'https://api.deepl.com/v2/translate' \
--header 'Authorization: DeepL-Auth-Key [yourAuthKey]' \
--header 'Content-Type: application/json' \
--data '{
  "text": [
    "The table is green. The chair is black."
  ],
  "target_lang": "DE"
}'
Example response
{
  "translations": [
    {
      "detected_source_language": "EN",
      "text": "Der Tisch ist grün. Der Stuhl ist schwarz."
    }
  ]
}

Translating Large Volumes of Text

There are a few methods to translate larger volumes of text:

  • If your text is contiguous, you can submit whole paragraphs to be translated in one request and with one text parameter. Prior to translation, your text will be split into sentences and translated accordingly.

  • The translate function can take several text parameters and will return translations of each such parameter separately in the same order as they are requested (see example below). Each of the parameter values may contain multiple sentences. Up to 50 texts can be sent for translation per request.

  • You can make parallel requests by calling the translate function from several threads/processes.

The example below uses our API Pro endpoint https://api.deepl.com. If you're an API Free user, remember to update your requests to use https://api-free.deepl.com instead.

Example request: large volumes of text
curl -X POST 'https://api.deepl.com/v2/translate' \
--header 'Authorization: DeepL-Auth-Key [yourAuthKey]' \
--header 'Content-Type: application/json' \
--data '{
  "text": [
    "This is the first sentence.",
    "This is the second sentence.",
    "This is the third sentence."
  ],
  "target_lang": "DE"
}'
Example response
{
  "translations": [
    {
      "detected_source_language": "EN",
      "text": "Das ist der erste Satz."
    },
    {
      "detected_source_language": "EN",
      "text": "Das ist der zweite Satz."
    },
    {
      "detected_source_language": "EN",
      "text": "Dies ist der dritte Satz."
    }
  ]
}

In-Text Markup

You should take precaution with uncommon characters you may have embedded in your texts. Uncommon character sequences, which may be recognized markers within your system, might get translated or removed, resulting in a corrupted structure. In this case, it is advisable to either split the text so that there is no need to send markers, or to convert your markers to XML tags and enable XML handling or HTML handling.

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