# Js Viewer Localization
This topic describes how to specify the UI language of the JS Viewer.
## Content
Js Viewer supports English, Japanese, and Chinese localizations for which the localized files are already available. This article discusses setting a Js Viewer UI language from the supported localizations and adding custom localization for the languages that are not explicitly supported.
### Set Js Viewer UI Language
To set the UI language of Js Viewer, specify the [Js Viewer API](/activereportsnet/docs/v20.1/developers/create-applications/js-viewer-application/jsviewer-api) while initializing the component. The supported values are 'en-US' (for English), 'ja-JP' (for Japanese), and 'zh-CN' (for simplified Chinese).
```html
```
### Add Custom Localization using Resource Strings
With the [Js Viewer NPM package](https://www.npmjs.com/package/@mescius/activereportsnet-viewer), you can access the resource strings from the **custom-locale.json** file available in the **activereportsnet-viewer\\dist** folder of the package. By default, the custom-locale.json file contains all the strings in English that are required to localize the viewer.
To add custom localization to the Js Viewer UI,
1. Copy the 'custom-locale.json' file to the 'wwwroot' folder and rename the file to, say, 'fr-locale.json'.
2. Open 'fr-locale.json' file and translate the strings in the file to any language, say French. For example, here we are localizing the Js Viewer component for French language, so the strings must be translated to French language.
```json
{
"viewer": {
"toolbar": {
"refresh": "Rafraîchir",
"cancel": "Annuler"
},
"search": {
"start-search-btn": "Recherche",
"paneltitle": "Recherche"
}
}
}
```
3. Specify the URL of 'fr-locale.json' file using the [Js Viewer API](/activereportsnet/docs/v20.1/developers/create-applications/js-viewer-application/jsviewer-api) to add localization to the viewer.
```html
```
> type=note
> **Note**: As you may notice, some of the localization strings are skipped in the above example. The values for which localization strings are missing are by default displayed using EN localization data.
An alternate approach is to use the [Js Viewer API](/activereportsnet/docs/v20.1/developers/create-applications/js-viewer-application/jsviewer-api) to directly assign the localized JSON to the viewer, as shown.
```html
```
## See Also
#### Developers
[Js Viewer API](/activereportsnet/docs/v20.1/developers/create-applications/js-viewer-application/jsviewer-api)