Thanks Claude for the response. I tried that but no luck. One thing I found while doing some research, it converts it into their respective language if we change device's language along with application language. So, maybe because they are native button outside the application and hence, it depends on the device's language. So, I tried that thing and now it is showing me the button title in Spanish after I change the device's language to Spanish and vice-versa.

Hello Claude, Thanks for then reply. Which buttons precisely ? Actions button. When you long press the notification. There comes action buttons. What is the iPhone language setting ? Language setting is English. However, project setting is Spanish. I do not find where you tried to ;localise those buttons ; if so, they are displayed in the language of settings. I localised it while add the local notification in UNUserNotificationCenter: let logNow = NSLocalizedString("Log Now", comment: "Alert") let logNowAction = UNNotificationAction(identifier: "LOG_NOW_ACTION", title: NSString.localizedUserNotificationString(forKey: logNow, arguments: nil),options: [.foreground]) UNNotificationCategory(identifier: "CATEGORY_REMINDERS", actions: [logNowAction], intentIdentifiers: [],                                 hiddenPreviewsBodyPlaceholder: "", options: .customDismissAction) notifyCenter.getNotificationCategories(completionHandler: { categories in             var allCategories = categories             self.notifyCenter.setNotificationCategories(allCategories)         })