Useful Commons

Free browser tool

Compare two JSON datasets by key

Paste an earlier and a later export as JSON arrays of flat records, name the identity key fields, and see what was added, removed or changed. Matching is exact and type-aware, so 4 and "4" differ. Starting from CSV? Convert each file with the CSV to JSON tool first.

Runs on this device. No upload, account or tracking; nothing is scheduled or applied.

Your snapshots

Before

UTF-8, up to 280,000 characters

    After

    UTF-8, up to 280,000 characters

      Matching

      Records with the same key values are paired.

      Have CSV files? Convert each one with CSV to JSON first; every cell stays text.

      Up to 5,000 flat records per snapshot and 100 fields per record. Missing, null, zero, false and empty text stay distinct. A large drop in coverage withholds removal details until you confirm.

      About this tool

      What this tool does

      Match two snapshots of JSON records by the key fields you choose and list exact additions, removals, changed fields and duplicate keys, without uploading them.

      Limits and safe use

      Up to 5,000 flat records per snapshot and 100 fields per record. Missing, null, zero, false and empty text stay distinct. A large drop in coverage withholds removal details until you confirm. Review the report before relying on it. It is a deterministic check, not a certification, and it does not send data to a server or a model.