Difference Between Localization Parameters in Actions

Last Updated: Feb 20, 2026

Overview

This article explains the difference between the following localization-related parameters available in Actions.

event.request.language
event.transaction.locale
event.transaction.ui_locales

Solution

event.request.language
- The languages requested by the browser. Namely, the ones specified in the Accept-Language header.
event.transaction.locale
- The locale that is used to display the page and process the transaction.
event.transaction.ui_locales
- The languages requested using the ui_locales query parameter. (i.e. /authorize?ui_locales=fr-FR)

The New Universal Login Page decides which language to present based on the language the browser requested (event.request.language), the one specified using query parameter (event.transaction.ui_locales,) and tenant-supported languages.

For more information about tenant-supported languages, please see Set tenant supported languages.