# Internationalization (i18n)
Halo themes support i18n via `.properties` files under an `i18n/` directory. Thymeleaf provides the `#messages` object for reading translations in templates.
---
## Directory Structure
```
my-theme/
├── i18n/
│ ├── default.properties # Fallback / default language
│ ├── zh_CN.properties # Simplified Chinese
│ ├── zh_TW.properties # Traditional Chinese
│ └── es.properties # Spanish
├── templates/
└── theme.yaml
```
> Halo uses `default.properties` as the fallback when no locale-specific file matches the user's preference.
---
## Properties File Format
Simple key-value pairs:
```properties
# default.properties
page.author.title=Author: {0}
common.previousPage=Previous
common.nextPage=Next
common.noPosts=No posts yet.
```
```properties
# zh_CN.properties
page.author.title=作者：{0}
common.previousPage=上一页
common.nextPage=下一页
common.noPosts=暂无文章。
```
Placeholders `{0}`, `{1}` ... are filled by the arguments passed to the message function.
---
## Using i18n in Templates
### `#messages.msg(key)` — Get a message
```html
```
### `#messages.msgOrNull(key)` — Get a message or null if missing
```html
```
### Thymeleaf shorthand `#{key}` — Standard expression
```html
Previous
```
---
## `#locale` — Current Locale
Useful for rendering language-specific UI or setting ``:
```html
```
---
## Frontend i18n Pattern
Some themes also need translations in JavaScript. A common pattern is to inject the needed strings into a global object via inline script:
```html
```
> Note: `[(#{key})]` is Thymeleaf's unescaped inlining syntax. It evaluates the expression and inserts the raw value into the script.
---
## Online Docs
https://raw.githubusercontent.com/halo-dev/docs/refs/heads/main/docs/developer-guide/theme/global-variables.md