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i18n Missing Key Finder - Online Compare Language Files

Developer Tools Internationalization i18n keys missing translation
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i18n Missing Key Finder

Compare your language JSON files instantly. Find missing translation keys, empty values, and extra keys across multiple locales.

Reference Language Base File
or drop / click to upload .json file
Keys: 0
Comparison Languages
Add one or more language files to compare against the reference.
Supports nested JSON structures with dot-notation keys

Frequently Asked Questions

What file formats are supported?
This tool supports JSON files with both flat and deeply nested structures. Keys are automatically flattened using dot notation (e.g., nav.menu.items.settings). If you use YAML, simply convert it to JSON using any online YAML-to-JSON converter before pasting. Most i18n frameworks (react-i18next, vue-i18n, Angular i18n, Laravel localization) use JSON as their primary format.
How does nested key comparison work?
Nested JSON objects are recursively flattened into dot-separated key paths. For example, {"header":{"title":"Welcome"}} becomes the key header.title. This matches how most i18n libraries resolve translation keys. The tool compares all flattened keys between your reference file and each comparison file to detect missing, empty, or extra keys.
What do the different status badges mean?
Missing — The key exists in the reference file but is completely absent from the comparison file.
Empty Value — The key exists but its value is an empty string "" or null.
Found — The key exists with a non-empty value in both files.
Extra Key — The key exists in the comparison file but not in the reference (potentially unused/legacy keys).
Can I compare more than 2 languages at once?
Yes! Click the "Add Language" button to add as many comparison files as you need. Each language gets its own tab in the results view. This is especially useful when managing a multilingual application with 5–10+ locales and you want to audit all of them against your primary reference file (usually English).
Is my data secure? Are files uploaded to a server?
Absolutely secure. All processing happens entirely in your browser using JavaScript. No data is ever uploaded, transmitted, or stored on any server. You can even disconnect your internet after the page loads and the tool will work perfectly. Your language files remain 100% private on your machine.
What i18n frameworks is this compatible with?
This tool works with any i18n framework that uses JSON-based translation files, including: react-i18next, vue-i18n, Angular i18n, Next.js i18n, Laravel JSON localization, FormatJS, Polyglot.js, and many more. As long as your translations are stored in JSON with key-value pairs (nested or flat), this tool has you covered.
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