Building an AI translator that lives everywhere on macOS, iOS and Chrome

Developer built Linguin, an AI translator with native macOS, iOS, and Chrome extension apps, designed to let users translate selected text without leaving their current app. The product uses a shared service contract for translation logic while each client maintains a platform-specific UX, and leverages LLMs for context-aware translations in 100+ languages.

Most translation tools make you leave what you're doing: copy text, switch to a tab or app, paste, read, copy back. I wanted translation to sit inside whatever I was already using. That turned into Linguin https://linguin.app , an AI translator with a native Mac app, an iPhone app, and a Chrome extension. Here's how I think about building the "same" product across three very different surfaces. The product promise is identical everywhere: select text, get a fast, context-aware translation in 100+ languages. But the interaction has to be native to each platform, or it feels wrong: Same core, three genuinely different UX shells. The translation logic - language detection, prompt construction, tone handling, caching - is the part you never want to fork. If Mac and iOS drift, you get subtly different translations for the same input, which erodes trust fast. So the model-facing logic lives behind one small service contract, and each client is a thin shell that owns only its platform UX. A translation request looks the same whether it comes from the menu bar, the share sheet, or a browser selection. Classic MT is great at literal accuracy but blind to context. "Book" in a travel app and "book" in a library app should not translate the same way. Passing the surrounding context and a tone hint formal, casual, technical to an LLM produces translations that read like a human wrote them, not a dictionary. The tradeoffs I had to design around: If you want to try it, the Mac app, iOS app and Chrome extension are all at https://linguin.app https://linguin.app Curious how others structure a shared core across native + web clients - do you go with a shared service, a shared package, or just accept some duplication?