I built a CLI to catch i18n bugs. It found 74 issues in my own app before they shipped

Francis Okocha-Ojeah — Sun, 10 May 2026 10:50:42 +0000

We ship a React Native app in English and Portuguese. Every other release, someone would find a hardcoded English string or a missing translation key. Manual audits were slow, inconsistent, and honestly, error-prone.

I was tired of it.

So I built locale-lint. A zero‑config CLI that scans your entire codebase and catches the stuff we usually miss.

I ran it on our production app. In less than half a second, it found 74 issues that I had completely overlooked. Keys that existed in English but not Portuguese. Labels that were still raw English. Stuff that would have shipped in the next release.

Here’s exactly what it flagged in our app:

What it detects

Missing keys — e.g. English key missing from Portuguese
Unused keys — can be safely cleaned up
Undefined keys — called in code but missing from all locale files
Hardcoded text — raw strings in JSX like <Text>Welcome</Text>
Interpolation mismatches — e.g. {{name}} in EN but {nome} in PT

Why I’m sharing this

If you’re building a React, Next.js, or React Native app with any of these libraries, this works out of the box:

i18next / react-i18next
next-intl
i18n-js
react-intl / FormatJS
vue-i18n

No config needed. Just run:

npx locale-lint check

It auto‑detects your locale files and source folders. Under 500ms even on a decently sized app. Exits with code 1 if issues are found, so you can throw it straight into CI.

It’s open source (MIT).

GitHub: https://github.com/francisojeah/locale-lint
npm: https://www.npmjs.com/package/locale-lint

Hopefully it saves someone else the same headache.

DEV Community: Francis Okocha-Ojeah

I built a CLI to catch i18n bugs. It found 74 issues in my own app before they shipped

What it detects

Why I’m sharing this