DeepL translation stopped working: Mandatory API update required (March 2025)

[voothi]

Description
A few days ago, the DeeplTranslator started failing with an AuthorizationException, even when using a valid API Key.

Traceback

Query error: The program has returned exit code 1.
Traceback (most recent call last):
  File "translate_deepl.py", line 31, in <module>
    result = translator.translate(args.text)
  File "deep_translator\deepl.py", line 87, in translate
    raise AuthorizationException(self.api_key)
deep_translator.exceptions.AuthorizationException: Unauthorized access with the api key ...

Cause
This issue is caused by the DeepL API breaking changes (effective March 2025) which have deprecated:

1. GET requests for translation (now requires POST).
2. The auth_key query parameter (now requires Authorization header).

Reference
DeepL Breaking Changes Notice

Proposed Solution
The DeeplTranslator.translate method needs to be updated to use requests.post and send the API key via the Authorization: DeepL-Auth-Key [KEY] header.

[voothi]

The error trace confirms the issue originates in deep_translator.deepl raising an AuthorizationException.

• Related Issue: deep-translator#299
• Upstream PR: deep-translator#303
  The linked GitHub issue confirms that deep-translator versions prior to the fix use the deprecated method.
  DeepL API documentation confirms the deprecation of GET requests for translation.