DeepL Python Library

The DeepL API is a language
translation API that allows other computer programs to send texts and documents to DeepL's servers and receive
high-quality translations. This opens a whole universe of opportunities for developers: any translation product you can
imagine can now be built on top of DeepL's best-in-class translation technology.

The DeepL Python library offers a convenient way for applications written in Python to interact with the DeepL API. We
intend to support all API functions with the library, though support for new features may be added to the library after
they’re added to the API.

Getting an authentication key

To use the DeepL Python Library, you'll need an API authentication key. To get a key, please create an account here. You can translate up to 500,000 characters/month for free.


The library can be installed from PyPI using pip:

pip install --upgrade deepl

If you need to modify this source code, install the dependencies using poetry:

poetry install


The library is tested with Python versions 3.6 to 3.9.

The requests module is used to perform HTTP requests; the minimum is version 2.18.


import deepl

# Create a Translator object providing your DeepL API authentication key
translator = deepl.Translator("YOUR_AUTH_KEY")

# Translate text into a target language, in this case, French
result = translator.translate_text("Hello, world!", target_lang="FR")
print(result)  # "Bonjour, le monde !"
# Note: printing or converting the result to a string uses the output text

# Translate multiple texts into British English
result = translator.translate_text(["お元気ですか?", "¿Cómo estás?"], target_lang="EN-GB")
print(result[0].text)  # "How are you?"
print(result[0].detected_source_lang)  # "JA"
print(result[1].text)  # "How are you?"
print(result[1].detected_source_lang)  # "ES"

# Translating documents
    "Instruction Manual.docx",

# Check account usage
usage = translator.get_usage()
if usage.character.limit_exceeded:
    print("Character limit exceeded.")

# Source and target languages
for language in translator.get_source_languages():
    print(f"{language.code} ({})")  # Example: "DE (German)"

num_languages = sum([language.supports_formality
                     for language in translator.get_target_languages()])
print(f"{num_languages} target languages support formality parameter")


Logging can be enabled to see the HTTP-requests sent and responses received by the library. Enable and control logging
using Python's logging module, for example:

import logging


All module functions may raise deepl.DeepLException or one of its subclasses.
If invalid arguments are provided, they may raise the standard exceptions ValueError and TypeError.

Command Line Interface

The library can be run on the command line supporting all API functions. Use the --help option for
usage information:

python3 -m deepl --help

The CLI requires your DeepL authentication key specified either as the DEEPL_AUTH_KEY environment variable, or using
the --auth-key option, for example:

python3 -m deepl --auth-key=YOUR_AUTH_KEY usage

Note that the --auth-key argument must appear before the command argument. The recognized commands are:

Command Description
text translate text(s)
document translate document(s)
usage print usage information for the current billing period
languages print available languages

For example, to translate text:

python3 -m deepl --auth-key=YOUR_AUTH_KEY text --to=DE "Text to be translated."

Wrap text arguments in quotes to prevent the shell from splitting sentences into words.


The test suite depends on deepl-mock. Run it in another terminal while executing the tests, using port 3000. Set the mock-server listening port using the environment variable DEEPL_MOCK_SERVER_PORT.

Execute the tests using tox.