iOS 15 System-Wide Translation in Third-Party Apps

With iOS 15, Apple introduced system-wide text translation, allowing users to translate foreign text directly within almost any app without switching to a dedicated translation tool. This article explains the underlying mechanism of iOS 15's system-level translation, how it seamlessly integrates into third-party applications, and the exact steps to use it.

The Underlying Technology

System-wide translation in iOS 15 functions through native iOS UI frameworks rather than app-specific implementations. When developers build apps using standard iOS text elements—such as UITextView, WKWebView, or selectable UILabel components—the system automatically injects system commands into the text selection menu.

Because Apple tied the Translate service directly into the system's contextual menu (the edit menu that displays "Copy," "Select All," and "Share"), third-party developers do not need to write custom code or integrate external translation APIs. As long as text selection is permitted by the application, the translation functionality is inherently available.

On-Device Processing vs. Cloud Translation

The translation engine itself is powered by Apple's Translate app architecture. In iOS 15, this operates in two modes:

  • On-Device Mode: Users can download offline language packs through Settings > Translate > On-Device Mode. In this state, processing occurs locally via the Apple Neural Engine, ensuring privacy and allowing translations without an active internet connection.
  • Server-Based Mode: When offline packs are unavailable, the system securely routes the selected text to Apple’s servers for real-time processing and returns the result to the interface.

How to Use Translation in Third-Party Apps

  1. Select the Text: Open any third-party application (such as WhatsApp, Twitter, or Safari) and highlight the text you wish to translate by pressing and dragging the selection handles.
  2. Open the Context Menu: Tap the selected text to reveal the contextual popup menu. If "Translate" is not immediately visible, tap the right arrow button (>) to cycle through additional actions.
  3. Select Translate: Tap Translate.
  4. Interact with the Translation Card: A modal sheet slides up from the bottom of the screen displaying the detected language, the translation, and several controls:
    • Play Audio: Listen to the pronunciation of both the source and translated text.
    • Copy Translation: Copy the converted text to the clipboard.
    • Add to Favorites: Save the translation for later review in the native Translate app.
    • Change Language: Switch the output language dynamically without leaving the host app.

Limitations

The feature relies on native text rendering. Third-party apps that utilize custom rendering engines, web wrappers that suppress default contextual menus, or apps that present text inside static images will not display the native translation menu. However, for images containing text, iOS 15's companion feature, Live Text, provides an identical translation overlay directly from camera feeds and photos.