iOS 18: Apple's Translation API

activesludge breaks down iOS 18's Translation API with real-world demos that show how to eliminate copy-paste translation workflows. This is the most practical guide I've seen for implementing on-device translation.

Apple's new Translation API in iOS 18 lets developers embed translation directly into their apps with both system UI overlays and custom implementations. The author built a complete demo app showcasing legal disclaimers, real estate listings, contact forms, and surveys—all with in-app translation that works entirely on-device.

Key Takeaways

• Three implementation modes: overlay UI, replace text, or fully custom translation flows
• Batch translation processes multiple strings while preserving order using clientIdentifier
• All translations happen on-device after language packs download (no constant internet needed)
• Default config auto-detects source language and targets user's region or preferred language
• Gotcha: Custom UI features fail silently without Translate app installed (no way to check)

The article reveals an unexpected behavior about how the API determines target languages that could trip up your implementation if you're not careful.