Localization is the process of translating and adapting content to a specific language, region or culture.

Yarn scripts are written in human-readable language. This is generally a single language, and (most of the time) will be written in the language that your development team primarily speaks. The language that a Yarn project is written in is called the base language.

However, if you want your dialogue to be understood by people who don't speak this language, you will need to translate it. Yarn Spinner is designed to make it easy to extract the user-facing text of your dialogue into a strings file, which can then be translated into a different language, and then loaded at run-time. You can translate your project into as many languages as you'd like, and Yarn Spinner will handle it for you automatically.

Yarn Spinner is also designed around the idea that a line of dialogue may have assets associated with it. Most commonly, this means an audio file that contains an actor performing the line, so that it can be used in your game as a voice-over. These assets are also localisable.

I just want to add voiceover in a single language. Why do I need to localise, too?

The philosophy of Yarn Spinner's approach to localisation is: if you want your dialogue to be text-only, and in a single language, you don't need to do anything at all. If you want to do anything else, you will need to set up a localisation and manage it using Yarn Spinner's processes.

We've found that most users who want to start using Yarn Spinner want to quickly get dialogue on the screen, and don't want to do lots of work to get the basics going. That's why we make the simple use-case (text only, a single language) as easy to use as we can.

However, if you're building a game that's voice acted, it makes your life significantly easier if you build your systems with localisation in mind from the start. Additionally, if you have the resources to add voice-over to your project, you should also have the resources to translate your game to other languages (even if you only have voice-overs in a single language.)

To that end, we designed it so that voiceover is intimately tied to localisation, so that you have to at least start thinking about localisation at the start of the process.

Localisation Terminology

  • Localisation: A set of information that describes where to find text and assets for a given language.

  • Base language: The language that your Yarn script files are written in.

  • Strings file: A text document that contains translated versions of Yarn lines.

  • Line ID: A unique code that identifies a line of dialogue or an option in the original source text.

  • Localised line: The text of a line of dialogue, in a particular locale.

  • Localised line asset: An asset (for example, an audio clip) that's associated for a particular line, in a particular locale. For example, an audio clip containing the voiceover for the line "Hello there", in German.

Using Localization the Easy Way

We specify our supported localizations when creating the YarnSpinnerPlugin (or using deferred compilation):

YarnSpinnerPlugin::new().with_localizations(Localizations {
    base_localization: "en-US".into(),
    translations: vec!["de-CH".into()],

The base localization is the language in which your Yarn files are already written. In this case, we specified that our Yarn file was written in English as spoken in the USA. The translations are all languages you want to support. Here, we want to support German as spoken in Switzerland.

Put the code shown above into the example used in the Quick Start and run the game.

Now take a look at your Yarn file at assets/dialogue/example.yarn. You will see that your line of dialog will contain an autogenerated ID, for example:

# assets/dialogue/example.yarn
title: Start
- Hello World!
+ Hello World! #line:13032079 

This ID uniquely references this line across translations. For the sake of clarity, we will use diff highlighting throughout this chapter. In case you're not familiar with this look, for our purposes the red line started by "- " shows how the line looked like before a change, while the green line started by "+ " shows how the line looks like after the change. The "- " and "+ " are just visual indicators and not actually part of the files, so don't let that confuse you!

You will probably also have noticed a new file in your assets that was not there before, namely "de-CH.strings.csv":

This file is called a strings file, because it contains translations of each string of text of your Yarn files. Let's see what it contains:

de-CH,line:13032079,Hello World!,example.yarn,Start,4,7f83b165,

Since this is a CSV, let's open it in an application that renders the content as a table:

You can see that our line from before is in there! Notice how the id matches across the files.

This file will be populated with new entries as soon you change the Yarn files. Assuming that you are using hot reloading as described in the setup, run your app again in case you closed it or advanced the dialog. While you are greeted with the "Hello World!" message on screen, open the Yarn file and edit it. Let's add a new line:

# assets/dialogue/example.yarn
title: Start
Hello World! #line:13032079 
+ This is a brand new line of text

Save the file while the game is still running. You should see that our new line just got assigned an own line ID:

# assets/dialogue/example.yarn
title: Start
Hello World! #line:13032079
- This is a brand new line of text
+ This is a brand new line of text #line:10414042 

In case you can't see this, your editor might still have the old state of the file cached. It usually helps to change focus, tab out to another window, or closing and reopening the editor. The strings file should now also contain a new entry:

Let's translate some of this. Change the string "Hello World!" in this file to "Hallo Welt!", which is German, and save it:

The game will currently happily ignore this as by default it uses the base language, which means it will take its text straight from the Yarn files. But we can easily switch the language:

fn spawn_dialogue_runner(mut commands: Commands, project: Res<YarnProject>) {
    let mut dialogue_runner = project.create_dialogue_runner();
    dialogue_runner.set_language("de-CH"); // Use our translation

Run the game again and you should be greeted by this text:

Hurray! See how painless localization can be?


Languages are specified according to IETF BCP 47. You can add as many translations as you want. Each will receive an own strings file.

To switch languages at runtime, simply retrieve a DialogueRunner through a Bevy query inside a system. When you use DialogueRunner::set_language() as shown above, you will set the language for both text and assets. You can be more granular by using DialogueRunner::set_text_language() and DialogueRunner::set_asset_language() separately instead. This allows you to support use cases such as showing the text in the player's native language and play voiceover sound in the original recorded language, which might be a different one.


Since assets require using localization, they are searched for in folders named after the language they support. For the example used throughout this chapter, the assets for the base localization would be searched for in assets/dialogue/en-US/, while the assets for the de-CH translation will be searched at assets/dialogue/de-CH/. This is however more a convention than a rule, as a given AssetProvider is allowed to look for its assets wherever. The asset providers shipped by Yarn Spinner will additionally expect assets to be named after the line ID they belong to. For example, the AudioAssetProvider would look for the voice line reading our "Hello World!" line at assets/dialogue/en-US/13032079.mp3 for the base localization.

To read more about how to use assets, read the chapter Assets.

File Editing Workflow

The strings file can be freely edited by a translator in the text and comment fields. While you can translate the texts yourself, the format being straightforward allows the translator to also be someone else that is not involved with the coding part of the game at all.

You might have some questions regarding what happens when one person edits a Yarn file while another edits the strings file. As a general rule, the strings file will try to "keep up" with the Yarn file without ever destroying anything that was already translated.

As you've seen, new lines will be amended. If the Yarn file has a line edited, it will be changed in the strings file as well if it was not yet translated. If there is already a translation, it will be marked by a "NEEDS UPDATE" prefix in the text. If a line was deleted in the Yarn file, it will also be deleted in the strings file if it was untranslated. Otherwise, it will be left untouched.

Bottom line: if there's a translation, it will never be removed.

Shipping the Game

Once you want to build your game for a release, you should disable the automatic file creation and editing. To do this, add the following line to the plugin creation:

// ...

This will change the behavior of missing translations to simply fall back to the base localization.

While you're on it, you might also want to disable Bevy's hot reloading.


You may have wondered what the .into()s were for in the lines at the beginning of the chapter:

YarnSpinnerPlugin::new().with_localizations(Localizations {
    base_localization: "en-US".into(),
    translations: vec!["de-CH".into()],

They're here because a localization is not just a string with a language code, but an entire struct, namely Localization. You can construct this struct directly the path to the strings file and where assets are searched for.

Yarn Spinner® and Secret Lab® are trade marks of Secret Lab Pty. Ltd., and are used by Yarn Spinner Pty. Ltd. under license.