Jitsumu Lab — JSON Localization Check (Free Trial)

Check your translation JSON before release

A free browser checker for creators managing their own flat JSON translation files. Compare one source with one translation to find missing keys, extra keys, blank values and supported placeholder mismatches.

English and Japanese interface. The free version opens in English; use UI language / 表示言語 to switch to Japanese. Switching the interface language keeps your inputs, check results and filter settings. It does not translate your JSON, keys, text or file names.

Try it here

1. Launch the browser tool above.
2. Select Load fictional sample, then Check to see the example results.
3. Paste your own source and translation JSON, then select Check. File inputs are also provided; pasting is recommended in the embedded player.

The included fictional sample intentionally contains mismatches. Editing an input invalidates previous results; run Check again after edits. Changing only the UI language keeps the results. Clear inputs and results clears browser-held inputs and results without changing your original files.

The checker has no feature that sends your JSON, file names, keys or results to a server, and it does not call an AI service. Inputs and results stay in browser memory and are not automatically saved. Loading the hosted page and following external links use an internet connection; the hosts' conditions and infrastructure logs still apply.

Supported input and checks

• UTF-8 JSON objects with string values only; no arrays or nested objects.
• One source and one translation in this free version.
• Up to 1,048,576 bytes (1MiB) and 2,000 keys per input. The source must contain at least one key.
• Missing/extra keys, empty or whitespace-only values, and differences in the types and counts of supported placeholders. Blank source values are flagged too.
• Duplicate keys, invalid UTF-8/JSON and non-string values are rejected.

Example:

{"start":"Start","greeting":"Hello, {name}","score":"Score: %d"}

Supported placeholders: {name}, {0}, %s, %d, %1$s, %1$d. Named placeholders start with an ASCII letter or _, followed by ASCII letters, digits or _. Numbered printf positions start at 1. Placeholder types and counts are compared; reordering is allowed. %% is treated as literal text.

Limits

No CSV input, translation generation, grammar or meaning checks, engine integration, or in-game display checks. Nested JSON, i18next-style {{name}}, ICU, %f, printf width/precision and other unsupported formats are outside the supported scope. Some unsupported syntax is flagged for review; this is not a complete syntax validator.

The free browser version has no CSV export. The screen displays up to 200 matching rows and abbreviates long values. A result with no reported issue does not certify a translation or game as correct.

Need multiple translations and CSV export in the browser?

The downloadable edition on BOOTH is JPY 980, one-time purchase:

View the paid edition on BOOTH

• One source plus up to five translations per check.
• CSV export of all results and full text, including rows without findings, regardless of screen filters or the 200-row display limit.
• Japanese interface on first opening, with an English switch. CSV headings and findings use the selected UI language; your original data is not translated.
• A local HTML tool, fictional samples, a guide and license. No installation, API key or additional tool account is required.

The free browser tool and its downloadable HTML ZIP remain available without buying the paid browser edition. In the browser editions, checking multiple translations and saving CSV are the paid additions. The separate free CLI download below does include CSV/JSON for one translation.

License and checked environments

You may use the free version with data you are authorized to handle in your own commercial or noncommercial work, and share check results with your production team. Redistribution or resale of the tool is not allowed. The free version does not grant access to paid features. See the included license for details.

The paid license covers one individual or one legal entity using the tool for its own commercial or noncommercial work; internal use within that entity and sharing generated reports with the production team are allowed. Redistribution or resale of the tool or bundled files is prohibited. Custom translation work, customization and periodic updates are not included; individual support or updates are not guaranteed.

v1.1 checked in Windows Edge over local HTTP: English/Japanese switching with retained inputs/results/filters, actual source/translation file input and comparisons. The paid edition’s CSV download was also checked as an actual file. See the included README for details. File selection inside the itch.io iframe, direct file:// launch, other browsers/OS, physical mobile devices and game-engine integration remain unverified. Pasting JSON is recommended in the embedded player. Check the supported format and environment before choosing the paid edition.

日本語の案内

フラットな翻訳JSONのキー抜け・余分なキー・空欄・指定変数の種類や個数の違いを確認する無料ブラウザ体験です。原文1つ＋翻訳1つを比較します。ブラウザ体験版にはCSV保存はありません。下記の別配布の無料CLIでは1翻訳の全件CSV/JSONを保存できます。

無料版は英語表示で開きます。画面上部の「UI language / 表示言語」から日本語に切り替えられます。切り替えても入力・検査結果・絞り込み条件は保持します。入力した文章を翻訳する機能ではありません。

「架空サンプルを入れる」→「検査する」で指摘の出方を確認できます。UTF-8・フラット・全値文字列のJSON、各1MiB・2,000キーまでが対象です。翻訳の意味の正しさや、各ゲームエンジンへの適合は判定しません。

最大5翻訳のまとめ検査と全結果のCSV保存が必要な方は、上記のBOOTH買い切り版（980円）をご確認ください。有料版は日本語表示で開き、英語へ切り替えられます。CSVの見出し・指摘も選択中の表示言語で保存します。元のJSON・ファイル名・翻訳文は変更しません。

Free terminal CLI / 無料1翻訳CLI

Prefer commands? Download Free CLI v1 — 1 translation, full CSV + JSON, exit codes (Node required) below. It checks your own source JSON plus one translation, saves every comparison row and returns exit code 0 (no findings), 1 (findings/review) or 2 (input/I/O error). You can repeat it separately for each language. No purchase, npm install, API key or additional account is required.

Extract the ZIP and run in that folder: node check.mjs --source examples/source.json --translation examples/before/ja.json --out reports-before. The fictional before example gives 7 rows / 4 flagged / exit 1; using examples/after/ja.json with a different new output folder gives 6 rows / 0 flagged / exit 0. --out must be a new, nonexistent directory. Read README.md and LICENSE.txt first.

Requires Node.js 22 or later, not bundled. Actual testing: Windows / Node.js 24.19.0, local commands. Node.js 22, other OS and real CI hosts are untested. Same limited flat-JSON checks as the browser tool: string values only, at most 1MiB and 2,000 keys per input. No meaning, translation generation, engine integration or full ICU/i18next support. Inputs are not changed. The CLI has no network requests or third-party dependencies; OS/CI logs follow their own platform conditions.

無料CLIは原文1つ＋翻訳1つで、全件CSV/JSON保存・終了コード判定・反復実行を使えます。 Node.jsが必要です。自分のJSONでも利用可。無料1翻訳を言語ごとに繰り返すこともできます。最大5翻訳を一括判定して報告をまとめる有料CLIは、下記の別商品として公開しています。上記980円版は手動操作のブラウザ商品で、CLIではありません。ツール本体の再配布/転売は禁止、生成した報告は共有可。個別対応や将来更新は保証しません。

Need one combined run for up to five translations? / 最大5翻訳を一括検査したい方へ

The separate Batch CLI v1.0 on BOOTH costs JPY 2,980, one-time purchase. It adds up to five translations in one command and one combined CSV/JSON report set. The free CLI already includes repeated runs, full CSV/JSON and exit codes, and may be run separately for each language. The check rules and input limits are the same. If separate runs and reports suffice, use the free CLI. Node.js 22+ is required separately; actual checks are Windows/Node.js 24.19.0 only. Other OS, Node22 and real CI hosts remain untested.

有料一括CLI（2,980円）の追加価値は、最大5翻訳を1回で判定し、1組のCSV/JSONにまとめることです。無料CLIでも全件CSV/JSON・終了コード・言語ごとの反復実行ができます。検査精度や入力範囲は同じです。個別の検査・報告で足りる場合は無料版をご利用ください。CLIのライセンスは自身の作品・同一法人内の非公開repo/内部CI向けで、ツールの再配布や公開repoへの配置は禁止です。実CI運用・個別対応・将来更新は保証しません。

View Batch CLI v1.0 on BOOTH — JPY 2,980 / 有料一括CLIの内容と利用条件

AI use

AI was used to help create the code and documentation. The checker runs predefined rules in your browser; it does not use an AI service to process your translation files.

v1.1.1 input-safety fix / 入力の修正

v1.1.1 rejects unpaired Unicode surrogate characters in JSON keys or values before checking, preventing replacement characters in UTF-8 CSV. Valid emoji and correctly paired Unicode remain supported.

v1.1.1では、JSONのキーや値に含まれる対になっていないUnicodeサロゲート文字を検査前に拒否します。CSV保存時に置換文字へ変わることを防ぐ修正です。正しい組の絵文字やUnicode文字は利用できます。