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The DeepLX API returns translation results in a structured JSON format. All successful translations return an HTTP 200 status code with the complete DeepLXTranslationResult object.

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Response Structure

The response object contains the following fields:
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code
integer
required
HTTP status code indicating the result of the translation request. Returns 200 for successful translations.
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id
integer
required
Unique identifier for the translation request. This ID is randomly generated for each request and can be used for tracking purposes.
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data
string
required
The primary translated text. This is the main translation result returned by DeepL.
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alternatives
string[]
required
An array of alternative translations. DeepL may provide up to 3 alternative translations for the same input text, offering different phrasings or word choices.
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source_lang
string
required
The detected or specified source language code in ISO 639-1 format (e.g., “EN”, “DE”, “FR”). If the request specified auto or an empty source language, this field contains the automatically detected language.
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target_lang
string
required
The target language code in ISO 639-1 format (e.g., “EN”, “DE”, “FR”). This matches the language specified in the translation request.
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method
string
required
Indicates the translation method used. Possible values:
  • "Free" - Translation performed using the free DeepL API method
  • "Pro" - Translation performed using a DeepL Pro account with dl_session cookie
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message
string
Error or status message. This field is only present when an error occurs or when additional information needs to be conveyed. It is omitted in successful responses.

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Success Response Example

{
  "code": 200,
  "id": 8352948020,
  "data": "Hello, World!",
  "alternatives": [
    "Hi, World!",
    "Hello World!",
    "Greetings, World!"
  ],
  "source_lang": "DE",
  "target_lang": "EN",
  "method": "Free"
}

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Alternatives Array

The alternatives array provides additional translation options:
DeepLX requests up to 3 alternatives from the DeepL API by setting requestAlternatives: 3 in the translation request. The actual number of alternatives returned may vary depending on the input text and language pair.
The alternatives are extracted from the DeepL API response structure:
  1. The API response contains a texts array with translation results
  2. Each text object has an alternatives array field
  3. DeepLX extracts the text field from each alternative object
  4. Only non-empty alternative texts are included in the final response
If no alternatives are available, the array will be empty [].

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Language Detection

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source_lang
string
When automatic language detection is used (by specifying "auto" or an empty string for source_lang in the request), DeepLX uses the whatlanggo library to detect the input language.The detected language is then:
  1. Used in the translation request to DeepL
  2. May be overridden by DeepL’s own language detection
  3. Returned in the response’s source_lang field
If the DeepL API returns a detected language in the response (result.lang), it will override the initially detected language. This ensures the most accurate source language is reported.

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Method Field

The method field indicates which translation endpoint was used:
MethodDescriptionEndpoint
FreeUses the free DeepL translation service without authentication/translate, /v2/translate
ProUses DeepL Pro account with dl_session cookie for enhanced features/v1/translate
The method is determined by checking if a dl_session value was provided in the request. From translate/translate.go:201:
Method: map[bool]string{true: "Pro", false: "Free"}[dlSession != ""]

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