ReplyLingo

ReplyLingo — voice translation that keeps you connected.
Receive a voice message, translate it, and understand it in your language
Speak naturally in your language and let ReplyLingo prepare the reply.
Keep your translated conversations organized and easy to revisit.
ReplyLingo Pro unlocks unlimited translations, natural voices, and more.
app icon
Translate
Record
History
Paywall
settings

Inspiration

A lot of conversations happen through voice messages now. The problem is that a voice message in another language can completely stop a conversation.

I wanted to build something that felt as simple as sending a normal voice message — without making people copy text into a translator, type a reply, or constantly switch between apps.

That is where ReplyLingo came from.

The idea was simple: receive a voice message, understand it, reply naturally, and send the reply back in the other person's language.

What it does

ReplyLingo translates voice messages instead of just translating text.

You can share a voice message with ReplyLingo from WhatsApp. It detects the language, transcribes the message, translates it, and lets you listen to the translation.

Then you can speak your reply naturally in your own language. ReplyLingo translates your reply and generates a voice message in the recipient's language, ready to send back.

It also keeps your conversations in History, so previous translations and replies are easy to find again.

For users who need it more often, ReplyLingo Pro adds unlimited translations and premium voices.

How we built it

ReplyLingo was built as a mobile app using React Native and Expo.

The voice pipeline combines speech-to-text, translation, and text-to-speech. We use OpenAI for transcription and translation and ElevenLabs for natural voice generation.

RevenueCat handles the subscription and Pro experience.

The app also uses WhatsApp sharing so the experience can start from a voice message that someone has already received, rather than forcing them to manually upload files.

A big part of the work was making all of this feel like one simple flow instead of a collection of separate AI tools.

Challenges we ran into

The hardest part was not simply getting translation to work. It was making the whole voice pipeline reliable.

Audio formats were one of the biggest issues. Different recordings do not always arrive in the format expected by the transcription service, so we had to handle and convert audio correctly before sending it for processing.

We also spent a lot of time on the interaction between recording, translation, generated audio, and sharing. A technically working feature is not enough if the user has to think about what to do next.

Another challenge was making the UI feel lightweight even though a lot is happening behind the scenes.

Accomplishments that we're proud of

The biggest thing we're proud of is that ReplyLingo is not just a prototype.

The iOS version and Android version is already live on the App Store and Play Store and the core experience is working end-to-end.

You can start with a real voice message, translate it, speak a reply, generate that reply in another language, and send it back.

We are also really happy with how the app turned out visually. We wanted it to feel friendly and approachable rather than like a complicated translation tool.

And most importantly, the idea works in both directions — you can understand someone in their language and reply in yours.

What we learned

We learned that building an AI feature is only one part of building a good product.

The quality of the experience depends on everything around it — audio handling, waiting time, errors, permissions, navigation, feedback, and making the next action obvious.

We also learned a lot about working with real voice data rather than just testing with a few perfect audio files.

Most of all, we learned that a simple user experience can require a surprising amount of engineering behind the scenes.

What's next for ReplyLingo

The next step is to make ReplyLingo even more useful for everyday conversations.

We want to improve the speed and reliability of the voice pipeline, expand language support, improve the WhatsApp experience, and make conversations feel even more natural.

We also want to continue improving the Pro experience and eventually bring ReplyLingo to more platforms.

The goal is simple:

Language should never be the reason you stop talking to someone you care about.