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JSON to Excel (XLSX) Converter

Convert a JSON array of objects into an .xlsx spreadsheet with nested fields flattened to columns, a live table preview and optional CSV export, all offline.

Overview

Converts a JSON array of objects into an Excel .xlsx spreadsheet, flattening nested objects into dot-path columns such as address.city and showing a table preview before you download. It also exports the same table as CSV. The workbook is built in your browser with SheetJS, so the data is not uploaded to a conversion server.

How It Works

Paste JSON, open a .json file of up to 25 MB, or load the sample. The tool counts rows and columns and previews the first 50 rows. Set a file name and a sheet name of up to 31 characters, then click Download .xlsx to build the workbook, or use Download .csv and Copy CSV for a plain-text version of the same table.

Step-by-Step Usage Guide

  1. Paste a JSON array or open a .json export file.
  2. Check the preview table and the row and column counts.
  3. Enter a file name and a sheet name.
  4. Click Download .xlsx, or download or copy the CSV version instead.

Technical Specifications & Standards

Each top-level array item becomes one row. Nested objects are walked recursively and their leaves become columns named by their path, so { address: { city } } turns into address.city. The column list is the union of keys across all rows in first-seen order, which means an item with an extra field adds a column and the other rows get an empty cell there. Arrays of plain values are joined with a comma and a space, while arrays of objects are written into a single cell as JSON text, because spreading them over rows would duplicate the parent record. Numbers and booleans keep their type in the .xlsx file, so Excel can sum and filter them. Column widths are estimated from the header and the first 200 values. Sheet names have characters Excel rejects, such as slash, colon and brackets, replaced. The SheetJS library is fetched only when you click Download .xlsx, which keeps the page light until then.

Targeted Use Cases

  • Handing an API export to a colleague who works in Excel or Google Sheets.
  • Reviewing a MongoDB or Firestore JSON export as a sortable table.
  • Turning a JSON log sample into a spreadsheet for quick filtering.
  • Preparing product or user data for a bulk import template that expects XLSX.

Notes & Gotchas

  • Flatten deeply nested arrays in your source query when you need one row per child record.
  • Check the preview for unexpected columns, which usually reveal inconsistent keys.
  • Use the CSV download for tools that cannot open .xlsx files.

Frequently Asked Questions

How are nested JSON objects converted to columns?

Each nested leaf becomes its own column named with a dot path, such as address.city or billing.plan.id, so the spreadsheet stays one row per top-level item.

What happens to arrays inside each object?

Arrays of strings or numbers are joined into one cell separated by commas. Arrays of objects are stored in one cell as JSON text so no data is lost and rows are not duplicated.

Is my JSON uploaded to a server?

No. Parsing, flattening and building the .xlsx file all happen in your browser tab; the only download is the SheetJS script itself, fetched when you first export.

Is there a size limit?

Files up to 25 MB can be opened. Very large arrays work but take longer, because the whole workbook is built in memory; the preview shows only the first 50 rows to stay responsive.

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