Online Tool Store
i18n Key Coverage Checker
i18n Key Coverage Checker separates missing keys from placeholder mismatches, because only one of those crashes at runtime.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Developer
i18n Key Coverage Checker
Frontend preview — no upload or external service.
Coverage report
Base locale has 234 keys. Other locale is missing 12 keys and has 3 placeholder mismatches in interpolated strings.
How the i18n Key Coverage Checker works
- Paste the base locale file and the one you are checking against it.
- Fix missing keys first — those fall back to the base language or render the key itself, depending on your framework.
- Check the placeholder mismatches, which are the ones that crash at runtime rather than merely looking wrong.
FAQ
Why do placeholder mismatches matter most?
Because a missing key usually falls back to the base language, which looks wrong but works. A translation missing a placeholder the code passes, or adding one it does not, throws at render time in many i18n libraries.
What about keys only the translation has?
They are usually leftovers from removed features. Harmless, and worth removing — they make every future translation review longer and suggest coverage that no longer exists.
Should missing keys block a release?
It depends whether your fallback is acceptable. Falling back to English in a mostly-translated interface is often fine; falling back to a raw key like nav.settings.title never is.
How we compare
| Feature | Online Tool Store | A CLI script | An IDE plugin |
|---|---|---|---|
| Placeholder checking | ✓ | ✗ | ✓ |
| Both directions | ✓ | One way | ✓ |
| Nothing uploaded | ✓ | Local | ✗ |
| No install | ✓ | ✗ | ✓ |
i18n Key Coverage Checker separates missing keys from placeholder mismatches, because only one of those crashes at runtime.