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NDJSON Record Deduplicator

Data

Remove duplicate records from newline-delimited JSON (NDJSON/JSON Lines), either by exact structural equality or by a chosen key field, keeping the first occurrence

Paste NDJSON (one JSON value per line, the format streamed by log pipelines, bulk export APIs, and JSON Lines datasets) and remove duplicate records in one pass. With no key field, two lines only count as duplicates when their parsed JSON values are structurally identical down to key order. Give it a key field instead, like an id or event_id, and it dedupes on that field's value alone, keeping the first record it saw for each key and reporting exactly which line numbers got dropped.

ndjsonjson-linesdedupededuplicatedata-cleaning

How to use NDJSON Record Deduplicator

  • 1.Paste NDJSON content, one JSON value per line, into the input field.
  • 2.Optionally enter a key field name to dedupe by that field's value instead of comparing whole records.
  • 3.Copy the deduplicated output, and check the removed line numbers if you need to audit what got dropped.

Frequently asked questions

What counts as a duplicate if I don't give a key field?
Two lines are duplicates only when JSON.stringify-ing their parsed values produces the same string, so the same keys must also appear in the same order. A record with identical values but reordered keys is treated as distinct, matching how the underlying data was actually written rather than a semantic deep-equal.
Which occurrence does it keep when it finds a duplicate?
The first one. Every later line whose comparison key (the whole record, or just the key field's value) matches an earlier line is dropped, and its original line number is listed in the result.
What happens if a record is missing the key field I specified?
The tool returns an error naming the line number, rather than silently treating a missing field as a match or skipping the record. Every record must have the key field for key-based dedup to run.
Does this modify or reorder the surviving records?
No, kept lines are returned in their original order and original formatting (just trimmed of surrounding whitespace), not re-serialized or pretty-printed.

Use via API, SDK, or MCP

cURL# Free: 1,000 req/day · Pro: 10,000 req/day
curl -X POST https://api.utilix.tech/v1/tools/ndjson-dedup \
  -H "Authorization: Bearer utx_live_..." \
  -H "Content-Type: application/json" \
  -d '{"input": "{\"id\":1}\n{\"id\":2}\n{\"id\":1}"}'

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