This article discusses setting the WebViewer UI language.

The localization file for WebViewer is ar-webviewer-locale.json. This file is automatically added to the project in the grapecity.activereports.web\content folder when you install the MESCIUS.ActiveReports.Web NuGet package, which is required when using WebViewer. The 'ar-webviewer-locale.json' file contains English localization so that the user can use it as a template for their own localization.

To localize WebViewer, first translate all the resources in the 'ar-webviewer-locale.json' file. Once you have translated all the resources, you must specify the location of the 'ar-webviewer-locale.json' file in the WebViewer’s LocalizationJson property.

WebViewer1.LocalizationJson = File.ReadAllText(Server.MapPath("~") + " ar-webviewer-locale.json ");