TransLoop

Inspiration

Machine translation is everywhere, but people who don't read the target language have no way to tell whether the output actually says what they meant. A single wrong word in an email to a client, a sign for foreign visitors, or a message to a coworker can change the meaning completely — and you won't notice until it's too late.

What it does

TransLoop is a translation self-check app. You type what you want to say, tap Translate & Check, and TransLoop:

1. Translates your text into the target language.
2. Back-translates that translation blind — without ever seeing your original — so the check isn't biased by knowing what you meant.
3. Compares the back-translation with your original, sentence by sentence, and shows a traffic light:
   • Ready to use (green) — the meaning survived the round trip
   • Nuance may differ (yellow) — tone or politeness shifted
   • Meaning has changed (red) — a fact, number, or intent drifted, with an explanation and a suggested fix

You only need to look at the yellow and red parts.

My Dictionary turns your checked translations into a personal knowledge base. Save a term or phrase once and TransLoop reuses your wording automatically every time it comes up again — so over time the translations sound like you (or your company).

Supported languages: Japanese ⇄ English, Chinese (Simplified), Korean, Vietnamese. The app itself is fully localized in English and Japanese.

How we built it

• App: a single-page web app wrapped with Capacitor 8 for iOS (and Android), with native Sign in with Apple, Google Sign-In, and a guest mode so anyone can try it without an account.
• Backend: Cloudflare Workers + D1. The translation pipeline runs three separate LLM calls (translate → blind back-translate → diff/verdict) with fail-closed validation of the model output.
• Privacy: the text you check is never stored on our servers; history lives only on your device.
• Monetization with RevenueCat: the RevenueCat SDK (purchases-capacitor) powers two auto-renewing subscriptions — TransLoop Premium (Monthly) and (Annual) — in one offering with a single premium entitlement. The paywall shows each plan's localized priceString straight from RevenueCat and calculates the annual saving in a currency-neutral way. RevenueCat webhooks (HMAC-signature verified) update the user's plan on our backend, so limits are enforced server-side and purchases restore across devices via our own user IDs.

Business model

• Free: 5 checks/day, 500 characters per check, 50 dictionary entries
• Premium: 100 checks/day, 2,000 characters per check, unlimited dictionary — monthly or annual (annual ≈ 2 months free)

Challenges we ran into

• Making the back-translation truly blind and getting the model to judge meaning drift consistently (not flagging harmless rewording) took many iterations of prompts and output validation.
• Shipping a Capacitor app to the App Store as a solo developer: signing without registered devices, entitlements for Sign in with Apple, and App Review's subscription disclosure rules (Guideline 3.1.2).
• Localizing everything — app UI, store listing, screenshots, and legal pages — into English for launch in the US.

What's next

• Android release on Google Play (in closed testing now)
• More language pairs and team dictionaries for small businesses

Try it (Premium for judges)

Both Premium plans include a 7-day free trial for new subscribers: install the app, open Settings, choose Monthly or Annual, and confirm the trial. Cancel any time in iOS Settings > Apple ID > Subscriptions.

RevenueCat Project ID

proj62a63a96

Note

The demo video shows version 1.3 of the app (free-trial labels and English issue labels), which is in App Review at the time of submission; the live App Store version is 1.2.

Built With

• back-translation
• capacitor
• cloudflare-workers
• ios
• revenuecat
• translation