DeepL Ruby 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 Ruby library offers a convenient way for applications written in Ruby 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 Ruby Library, you'll need an API authentication key. To get a key, please create an account here. With a DeepL API Free account you can translate up to 500,000 characters/month for free.

Installation

Install this gem with

gem install deepl-rb
# Load it in your ruby file using `require 'deepl'`

Or add it to your Gemfile:

gem 'deepl-rb', require: 'deepl'

Usage

Setup an environment variable named DEEPL_AUTH_KEY with your authentication key:

export DEEPL_AUTH_KEY="your-api-token"

Alternatively, you can configure the API client within a ruby block:

DeepL.configure do |config|
  config.auth_key = 'your-api-token'
end

You can also configure the API host and the API version:

DeepL.configure do |config|
  config.auth_key = 'your-api-token'
  config.host = 'https://api-free.deepl.com' # Default value is 'https://api.deepl.com'
  config.version = 'v1' # Default value is 'v2'
end

Available languages

Available languages can be retrieved via API:

languages = DeepL.languages

puts languages.class
# => Array
puts languages.first.class
# => DeepL::Resources::Language
puts "#{languages.first.code} -> #{languages.first.name}"
# => "ES -> Spanish"

Note that source and target languages may be different, which can be retrieved by using the type option:

puts DeepL.languages(type: :source).count
# => 24
puts DeepL.languages(type: :target).count
# => 26

All languages are also defined on the official API documentation.

Note that target languages may include the supports_formality flag, which may be checked using the DeepL::Resources::Language#supports_formality?.

Translate

To translate a simple text, use the translate method:

translation = DeepL.translate 'This is my text', 'EN', 'ES'

puts translation.class
# => DeepL::Resources::Text
puts translation.text
# => 'Este es mi texto'

Enable auto-detect source language by skipping the source language with nil:

translation = DeepL.translate 'This is my text', nil, 'ES'

puts translation.detected_source_language
# => 'EN'

Translate a list of texts by passing an array as an argument:

texts = ['Sample text', 'Another text']
translations = DeepL.translate texts, 'EN', 'ES'

puts translations.class
# => Array
puts translations.first.class
# => DeepL::Resources::Text

You can also use custom query parameters, like tag_handling, split_sentences, non_splitting_tags or ignore_tags:

translation = DeepL.translate '<p>A sample</p>', 'EN', 'ES',
                              tag_handling: 'xml', split_sentences: false,
                              non_splitting_tags: 'h1', ignore_tags: %w[code pre]

puts translation.text
# => "<p>Una muestra</p>"

To translate with context, simply supply the context parameter:

translation = DeepL.translate 'That is hot!', 'EN', 'ES',
                              context: 'He did not like the jalapenos in his meal.'

puts translation.text
# => "¡Eso es picante!"

The following parameters will be automatically converted:

Parameter	Conversion
preserve_formatting	Converts false to '0' and true to '1'
split_sentences	Converts false to '0' and true to '1'
outline_detection	Converts false to '0' and true to '1'
splitting_tags	Converts arrays to strings joining by commas
non_splitting_tags	Converts arrays to strings joining by commas
ignore_tags	Converts arrays to strings joining by commas
formality	No conversion applied
glossary_id	No conversion applied
context	No conversion applied

Glossaries

To create a glossary, use the glossaries.create method. The glossary entries argument should be an array of text pairs. Each pair includes the source and the target translations.

entries = [
  ['Hello World', 'Hola Tierra'],
  ['car', 'auto']
]
glossary = DeepL.glossaries.create 'Mi Glosario', 'EN', 'ES', entries

puts glossary.class
# => DeepL::Resources::Glossary
puts glossary.id
# => 'aa48c7f0-0d02-413e-8a06-d5bbf0ca7a6e'
puts glossary.entry_count
# => 2

Created glossaries can be used in the translate method by specifying the glossary_id option:

translation = DeepL.translate 'Hello World', 'EN', 'ES', glossary_id: 'aa48c7f0-0d02-413e-8a06-d5bbf0ca7a6e'

puts translation.class
# => DeepL::Resources::Text
puts translation.text
# => 'Hola Tierra'

translation = DeepL.translate "I wish we had a car.", 'EN', 'ES', glossary_id: 'aa48c7f0-0d02-413e-8a06-d5bbf0ca7a6e'

puts translation.class
# => DeepL::Resources::Text
puts translation.text
# => Ojalá tuviéramos un auto.

To list all the glossaries available, use the glossaries.list method:

glossaries = DeepL.glossaries.list

puts glossaries.class
# => Array
puts glossaries.first.class
# => DeepL::Resources::Glossary

To find an existing glossary, use the glossaries.find method:

glossary = DeepL.glossaries.find 'aa48c7f0-0d02-413e-8a06-d5bbf0ca7a6e'

puts glossary.class
# => DeepL::Resources::Glossary

The glossary resource does not include the glossary entries. To list the glossary entries, use the glossaries.entries method:

entries = DeepL.glossaries.entries 'aa48c7f0-0d02-413e-8a06-d5bbf0ca7a6e'

puts entries.class
# => Array
puts entries.size
# => 2
pp entries.first
# => ["Hello World", "Hola Tierra"]

To delete an existing glossary, use the glossaries.destroy method:

glossary_id = DeepL.glossaries.destroy 'aa48c7f0-0d02-413e-8a06-d5bbf0ca7a6e'

puts glossary_id
# => aa48c7f0-0d02-413e-8a06-d5bbf0ca7a6e

You can list all the language pairs supported by glossaries using the glossaries.language_pairs method:

language_pairs = DeepL.glossaries.language_pairs

puts language_pairs.class
# => Array
puts language_pairs.first.class
# => DeepL::Resources::LanguagePair
puts language_pairs.first.source_lang
# => en
puts language_pairs.first.target_lang
# => de

Monitor usage

To check current API usage, use:

usage = DeepL.usage

puts usage.character_count
# => 180118
puts usage.character_limit
# => 1250000

Translate documents

To translate a document, use the document.translate_document method. Example:

DeepL.document.translate_document('/path/to/spanish_document.pdf', '/path/to/translated_document.pdf', 'ES', 'EN')

The lower level upload, get_status and download methods are also exposed, as well as the convenience method wait_until_document_translation_finished on the DocumentHandle object, which would replace get_status:

doc_handle = DeepL.document.upload('/path/to/spanish_document.pdf', 'ES', 'EN')
doc_status = doc_handle.wait_until_document_translation_finished # alternatively poll `DeepL.document.get_status`
# until the `doc_status.successful?`
DeepL.document.download(doc_handle, '/path/to/translated_document.pdf') unless doc_status.error?

Handle exceptions

You can capture and process exceptions that may be raised during API calls. These are all the possible exceptions:

Exception class	Description
DeepL::Exceptions::AuthorizationFailed	The authorization process has failed. Check your auth_key value.
DeepL::Exceptions::BadRequest	Something is wrong in your request. Check exception.message for more information.
DeepL::Exceptions::DocumentTranslationError	An error occured during document translation. Check exception.message for more information.
DeepL::Exceptions::LimitExceeded	You've reached the API's call limit.
DeepL::Exceptions::QuotaExceeded	You've reached the API's character limit.
DeepL::Exceptions::RequestError	An unkown request error. Check exception.response and exception.request for more information.
DeepL::Exceptions::NotSupported	The requested method or API endpoint is not supported.
DeepL::Exceptions::RequestEntityTooLarge	Your request is too large, reduce the amount of data you are sending. The API has a request size limit of 128 KiB.
DeepL::Exceptions::ServerError	An error occured in the DeepL API, wait a short amount of time and retry.

An exampling of handling a generic exception:

def my_method
  item = DeepL.translate 'This is my text', nil, 'ES'
rescue DeepL::Exceptions::RequestError => e
  puts 'Oops!'
  puts "Code: #{e.response.code}"
  puts "Response body: #{e.response.body}"
  puts "Request body: #{e.request.body}"
end

Logging

To enable logging, pass a suitable logging object (e.g. the default Logger from the Ruby standard library) when configuring the library. The library logs HTTP requests to INFO and debug information to DEBUG. Example:

require 'logger'

logger = Logger.new(STDOUT)
logger.level = Logger::INFO

deepl.configure do |config|
  config.auth_key = configuration.auth_key
  config.logger = logger
end

Proxy configuration

To use HTTP proxies, a session needs to be used. The proxy can then be configured as part of the HTTP client options:

client_options = HTTPClientOptions.new({ 'proxy_addr' => 'http://localhost', 'proxy_port' => 80 })
deepl.with_session(client_options) do |session|
  # ...
end

Anonymous platform information

By default, we send some basic information about the platform the client library is running on with each request, see here for an explanation. This data is completely anonymous and only used to improve our product, not track any individual users. If you do not wish to send this data, you can opt-out by setting the send_platform_info flag in the configuration to false like so:

deepl.configure({}, nil, nil, false) do |config|
  # ...
end

You can also complete customize the User-Agent header like so:

deepl.configure do |config|
  config.user_agent = 'myCustomUserAgent'
end

Sending multiple requests

When writing an application that send multiple requests, using a HTTP session will give better performance through HTTP Keep-Alive. You can use it by simply wrapping your requests in a with_session block:

deepl.with_session do |session|
  deepl.translate(sentence1, 'DE', 'EN-GB')
  deepl.translate(sentence2, 'DE', 'EN-GB')
  deepl.translate(sentence3, 'DE', 'EN-GB')
end

Writing a plugin

If you use this library in an application, please identify the application by setting the name and version of the plugin:

deepl.configure({}, 'MyTranslationPlugin', '1.0.1') do |config|
  # ...
end

This information is passed along when the library makes calls to the DeepL API. Both name and version are required. Please note that setting the User-Agent header via deepl.configure will override this setting, if you need to use this, please manually identify your Application in the User-Agent header.

Integrations

Ruby on Rails

You may use this gem as a standalone service by creating an initializer on your config/initializers folder with your DeepL configuration. For example:

# config/initializers/deepl.rb
DeepL.configure do |config|
  # Your configuration goes here
end

Since the DeepL service is defined globally, you can use service anywhere in your code (controllers, models, views, jobs, plain ruby objects… you name it).

i18n-tasks

You may also take a look at i18n-tasks, which is a gem that helps you find and manage missing and unused translations. deepl-rb is used as one of the backend services to translate content.

Development

Clone the repository, and install its dependencies:

git clone https://github.com/DeepLcom/deepl-rb
cd deepl-rb
bundle install

To run tests (rspec and rubocop), use

bundle exec rake test

Caution: Changing VCR Tests

If you need to rerecord some of the VCR tests, simply setting record: :new_episodes and rerunning rspec won't be enough in some cases, specifically around document translation (due to its statefulness) and glossaries (since a glossary ID is associated with a specific API account). For example, there are document translations tests that split up the upload, get_status and download calls into separate test cases. You need to first rerecord the upload call, you can do execute a single test like this (the line should be where the it block of the test starts):

rspec ./spec/api/deepl_spec.rb:152

This will return a document_id and a document_key, you will need to update the values in the get_status and download tests accordingly. You can find examples for this in the git history. Similarly, for the glossary tests you will need to delete the recorded HTTP requests for certain glossary IDs so that rspec will create the glossaries on your account instead. Feel free to reach out on our discord if you run into any trouble here.

Acknowledgements

This library was originally developed by Daniel Herzog, we are grateful for his contributions. Beginning with v3.0.0, DeepL took over development and officially supports and maintains the library together with Daniel.