JSON Remove Duplicates

JSON deduplication removes duplicate data from JSON. Two modes: (A) Array dedup — remove duplicate items from a JSON array using deep equality (compare structure and values) or by a specific key (e.g., keep one item per unique "id"). (B) Key dedup — identify and optionally remove duplicate keys in JSON objects. Standard JSON allows only one value per key; duplicate keys (e.g., {"a": 1, "a": 2}) cause parsers to keep one value. This tool shows which keys are duplicated and lets you choose first-wins or last-wins.

All processing runs in your browser. Your data never leaves your device.

Paste your JSON. For array dedup: ensure input is a JSON array. Choose deep equality or by key (type the key name). Select keep first or keep last occurrence. Click Process. The tool shows original count, unique count, and duplicates removed.

For key dedup: ensure input is a JSON object. The tool lists duplicate keys found. Toggle remove duplicates and choose first-wins or last-wins. Copy the cleaned output. All processing is client-side.

Array dedup is useful for API responses that return duplicate records, merged lists, or log data with repeated entries. Key dedup helps when concatenating JSON objects, fixing malformed output, or normalizing config files. Use this tool before storing, diffing, or processing JSON to ensure clean data.