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If you want to localize Mastodon into your language, here is how.


There are two parts to Mastodon, the server and the web client. The translations for the web client are in app/javascript/mastodon/locales. For the server-side, the translations live in config/locales and are divided into different files. In addition, email templates for the server are found in app/views/user_mailer. Here are all the files you'll need to translate:

Original file (English) Location Description
en.json app/javascript/mastodon/locales/en.json Strings for the web client
en.yml config/locales/en.yml Strings for general use
simple_form.en.yml config/locales/simple_form.en.yml Strings for the settings area
devise.en.yml config/locales/devise.en.yml Generic strings for Devise
doorkeeper.en.yml config/locales/doorkeeper.en.yml Generic strings for Doorkeeper
Account confirmation message for Devise
Password change notification for Devise
Password reset instructions for Devise


Obtain the Source Code

If you use Github, first fork the Mastodon repository to your account. Then clone it to your local machine for further work.

For detailed instructions, you may read our Github cheatsheet.


  1. Duplicate the files in their folder and replace en in the filenames with your language's standard two-letter ISO 639-1 code. Or RFC5646 language tags for regional languages.

    For instance simple_form.en.yml becomes in the Spanish translation, and simple_form.zh-HK.yml in the Traditional Chinese (HK) translation.

  2. Also replace the language code in the first lines of all the files, and the last line of the .js file.

  3. Translate the right-side values from English to your language. Keep the indentation and punctuation.

Since Devise and Doorkeeper are popular libraries, there may already be translation files for your language available on the Internet. Devise's Wiki and doorkeeper-i18n are official sources for these translations, respectively.

Declaring the language

The locales are mentioned in several other files. To activate your translation, add your language code to the different lists present in these files:

File Location Comment
index.js app/javascript/mastodon/locales/index.js 2 lines to add
mastodon.js app/javascript/mastodon/containers/mastodon.js 1 line to add + 1 list to complete
settings_helper.rb app/helpers/settings_helper.rb 1 line to add + your language's name
application.rb config/application.rb 1 list to complete

Sending the translation

You can then push the files to git and submit a pull request.

For detailed instructions, you may read our Github cheatsheet.

Testing the translation

Once the pull request is accepted, wait for the code to be deployed on a Mastodon instance. Log-in with your account there, and change the locale in the settings. Browse and use the website. See if everything makes sense in context and if anything seems out of place or breaks the layout. Invite other Mastodon users speaking your language to try it and give feedback. Make changes accordingly and update the translation.

Updating the translation

Keep an eye on the original English files in app/javascript/mastodon/locales and config/locales. When they are updated, pass on the changes to your language files. For new strings, add the new lines to the same position and translate them. Once you're finished with the updates, you can submit a new pull request.


Appendix A. Plural handling

Different languages use different plural forms to be taken care of by Mastodon.

For JavaScipt (.js) translations, this is done in react-intl, by doing:

Here {appleCount, plural, one {is an apple} other {are {appleCount} apples}}.

On the other hand, .yml files are processed by rails-i18n. Items that look like this are pluralized fields:

  one: You ate an apple.
  other: You ate %{count} apples.

In both examples you can see a one case and an other case described for the pluralized strings. The exact strings is chosen by how many a certain quantity is -- when there is exactly one of something, the sentence goes to the one case; otherwise it goes to the other case. This how pluralization works for English (en) and a few other languages.

There are, however, many languages that don't operate in the one-other way. Polish has four plural forms, named one, few, many, and other respectively. Arabic has six. Chinese, Japanese, and Korean only have one form called other. If your language does not use one/other plural forms, be sure to check out the cardinal part of this Unicode CLDR Plural Rules chart. Also as a rule of thumb, always start translating with the other case in the English files as they are better generalized than the one case.

Appendix B. Command Tools

We have command line tools to help translators in their tasks. They are not essential. But they are really helpful.

To use the tools, you'd need to properly setup your work station.


You need to have Ruby and NodeJS setup in your machine. If you want to keep your global paths clean, you may use rvm and nvm.

You'd also need to install yarn with your nodejs setup.

To install Ruby with rvm:

gpg --keyserver hkp:// --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3
\curl -sSL | bash -s stable

To install nodejs and yarn with nvm:

curl -o- | bash
source ~/.bashrc
npm install stable
npm install -g yarn

Update node packages and ruby gems

You'll need to run these command in the root of your source code folder:

bundle install
yarn install

Server Translation

For the Ruby-based server, i18n Tasks is used to manage the translations.

The command:

bundle exec i18n-tasks [command] [options]

You can use this command to find all usages:

bundle exec i18n-tasks --help
Key Usages

To see if there is any missing or unused language key(s) in your language, you can use health command. For example, if you want to check the health of Magyar (hu) translations:

bundle exec i18n-tasks health hu

If you found that there is missing keys in your file, you can use add-missing:

bundle exec i18n-tasks add-missing hu

Please note that health would simply check the existence of the language key. It does not check if they are different from the default (English). Also the command add-missing only copy the English translation for your language.

In short, running add-missing can help you pass the health test, but you'd still need to check your yml and translate the "added" strings.

Web Client Translation

For web client, NPM scripts are written to help.

There are 2 specific scripts that you'll have to use:

yarn build:development

Build the webpack assets for development use. Also generate the frontend translation reference files. You'll need to run this every time you clone / fetch the source code.

You'll need to run this before using yarn manage:translations.

yarn manage:translations

Based on react-intl-translations-manager. Sync and check the translation strings. It will:

  • automatically create missing keys in json translation files; and
  • remove obsoleted translations; and
  • show you a list of translations needed; and
  • create non-existed translation files (if forced to).

You may use the help command to get usage instructions:

yarn manage:translations --help
Key Usages

You may specify the language to sync and check:

yarn manage:translations [language code]

For example, to synchronize translations for French (fr):

yarn manage:translations fr

You may also use this to create json language files. You'd need to apply the --force option. For example, if Arabic (ar) javascript translation were not created yet:

yarn manage:translations --force ar

will create the following language files:

  • app/javascript/mastodon/locales/ar.json
  • app/javascript/mastodon/locales/whitelist_ar.json

Check Your Translations

To see if your language is doing good, you may mix using the command tools, like this:

bundle exec i18n-tasks health zh-HK
yarn manage:translations zh-HK

If you're doing good, you'd have a result like this:

$ bundle exec i18n-tasks health zh-HK
Forest (zh-HK) has 422 keys in total. On average, values are 13 characters long, keys have 3.2 segments.
✓ Good job! No translations are missing.
✓ Well done! Every translation is in use.

$ yarn manage:translations zh-HK
yarn manage:translations v0.23.4
$ node ./config/webpack/translationRunner.js zh-HK
Maintaining zh-HK.json:

 Perfectly maintained, no remarks!

Done in 0.24s.