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JSON Array Indexer
Turn an array of JSON records into a lookup object keyed by one exact string member, rejecting duplicate or missing keys.
UTF-8 JSON array file, Pasted strict JSON array
JSON lookup object
Browser only
Runs locally in your browser. Your files, pasted content and generated output are not uploaded. Reset clears this tool’s working data.
This tool needs JavaScript. If it does not load, refresh the page and try again.
How to use this tool
- Paste a root JSON array of objects or choose a JSON file.
- Enter Exact index field name; the default is id, and an explicitly empty field name is allowed.
- Select Create lookup map and download lookup-map.json.
Examples
[{"id":"a","value":1e400}] becomes {"a":{"id":"a","value":1e400}} without converting the numeric token.
Limitations
- 5 MiB input, 50,000 records, depth 40, 200,000 parsed nodes, 1,000 UTF-16 units per field name, 10,000 per index value, 10,000 UTF-16 units per numeric token, 20 MiB output and 30 seconds.
- Integer-looking object keys may enumerate before others. Decoded records and numeric tokens are retained; source member order, whitespace and escape spellings are not promised.
- No JSONPath, inferred keys, numeric-key coercion or first/last-wins overwrite mode. Empty array produces an empty object.
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