JSON group by field

Client

Turn a flat array of objects into an object whose keys are field values and whose values are arrays of matching rows—handy for quick aggregation before export or mock data.

Learn more: grouping array rows

Collect each object in a root array under a key taken from one property value—output is an object mapping those keys to arrays of rows.

Versus sort or unique

Grouping keeps every row in buckets. Unique-by collapses duplicates; sort reorders the flat list without changing membership.

Key strings

Object and array field values become JSON strings in group keys. Missing properties use (missing).

Nearby workflows on Toolcore

  • JSON unique by field — Deduplicate JSON array rows by one field—keep first or last; local only. once JSON text parses on this page.
  • Sort JSON array by field — Sort a JSON array of objects by one property—asc or desc; local only. once JSON text parses on this page.
  • JSON pick or omit keys — Keep or drop top-level keys on an object or array of objects—case-sensitive; local only. once JSON text parses on this page.
  • JSON formatter — JSON format online: pretty-print, minify, validate, escape, download . once JSON text parses on this page.

Group array by field

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Root must be an array of objects. Each object is placed under a key derived from the chosen field value—missing fields use (missing).

2 groups.

Common use cases

  • Bucket API list results by status, category, or tenant before exporting to files.
  • Build quick histogram-style views from flat event arrays without a spreadsheet.
  • Prepare grouped fixtures for UI mocks where each key maps to a list of rows.

Common mistakes to avoid

  • Expecting nested grouping

    Only one top-level field is used. Multi-level pivots need repeated passes or a query tool.

  • Using non-object array elements

    Every row must be a plain JSON object. Primitives or nested arrays at the root are rejected.

FAQ

How are missing fields grouped?

Objects without the chosen property land under a "(missing)" key.

Is data uploaded?

No. Parsing and grouping run entirely in your browser.

How is this different from unique-by or sort?

Group by keeps every row in buckets. Unique-by collapses duplicates; sort reorders the flat array.

Common search terms

Phrases people search for that match this tool. See the full long-tail keyword index.

  • json group by field
  • group json array by key
  • json lodash groupby online

More tools

Related utilities you can open in another tab—mostly client-side.