Lang (YC S19) – Internationalization Built for Devs

Hey HN! We’re Eric, Peter, and Abhi, founders of Lang ( We help developers quickly translate their apps into foreign languages by combining internationalization SDKs with a command-line interface that integrates directly with human translators.

Previously, we all worked on building internationalization and localization tooling for companies. In our experience, companies don’t think about translation until too late, and the tech debt builds up very fast. It’s a nightmare to receive a task that says “translate app into Spanish.” Choosing the right open-source framework, refactoring the entire codebase, and integrating with human translators is a massive effort. As engineers, we wanted to work on features - not putting every string in our codebase into a translations.json file. In our months of internationalization work, we couldn’t find a good all-in-one toolkit. So we built Lang.

Like other internationalization libraries, Lang gives you a tr() function. Wrap your strings with tr(), and we’ll show your users translations that correspond to their language settings at run-time. But how do you actually get the translations? Open-source frameworks like Polyglot.js stop here, but Lang doesn’t. Run “push,” and our command-line tool will parse your code files, find tr() calls, collect newly added strings, and send them to human translators for you. For JavaScript, we use Babel to construct an Abstract Syntax Tree (AST) of your code, and traverse the tree to find tr()’d strings. For a developer, this makes it simple to add/remove/update strings: just run “push” in your terminal. You can track the status of your translations on our dashboard, and when they’re done just run “pull.” We’ll generate a translation file for you, and connect it with our tr() function. You own the file - Lang doesn’t make any network requests for translations at run-time, and your translations always load, even if our service is down.

This works for static strings in the code, but what about dynamic content in the backend or database? We expose a function called liveTr(), which takes a string argument. The first time liveTr() sees an untranslated string, it will make a request to Lang to translate it and return the string in its original language. But the next time, it will fetch the translation on-demand. We’ve shipped liveTr() with built-in caching functionality to reduce the number of network requests. We also have self-hosted solutions for users with high uptime requirements. This is a common in-house feature companies build for internationalization, and we want to make it available to all devs.

Lang currently supports JavaScript and Typescript apps (React, React Native, Vue etc.) with closed betas for Django, Android, and iOS. Give us a try at - machine translations are free, so you can see your app in another language in minutes. If you use human translations, we charge $99 / month for our tooling, and 6-8 cents per word translated. A lot of our work is inspired by open-source, and we want to give back - if you’re building an open-source project or non-profit, ping us at [email protected] We’ll drop the monthly fee :)

The HN community builds amazing products, and we’re sure there are plenty of people here who have translated their apps - we’d love to hear your experiences in this area and your feedback on how we can improve!

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andrey azimov by Andrey Azimov