JSON to Excel Online Free — No Upload, Merged Cells, 7 Formats
Turn JSON into a presentation-ready .xlsx workbook in your browser — nested headers, merged cells, autofilter, frozen panes. No upload, no signup.
Paste a JSON array, or drag in a .json / .xlsx / .xls / .csv file. Processed entirely on this device.
How to convert JSON to Excel with merged cells and multi-level headers
- Paste a JSON array (or load one of the 9 built-in samples), or drop an .xlsx/.xls/.csv file to reverse-convert it to JSON first.
- Pick a mode: automatic headers, custom columns with groups and deep paths, or nested-array handling.
- Enable group merging, summary rows, number formats, autofilter or frozen header rows as needed.
- Preview the exact workbook (editable, with undo/redo), filter rows, then export to xlsx, csv, sql, md, html, yaml or xml.
If your JSON is wrapped (e.g. { "data": { "list": [...] }}), the tool suggests candidate array paths with one click.
Three ways to handle nested data
| Strategy | What it does | Typical use |
|---|---|---|
| Expand nested objects | Objects like user: {name, email} generate 2-row merged headers; values use deep paths a.b.c. | User profiles, denormalized API records |
| Flatten child arrays | Each child item becomes a row; parent cells merge vertically across the whole block. | Orders per customer, line items |
| JSON string / per-record sheets | The child array goes into one wrapped cell, or each record gets its own detail sheet. | Compact archives or per-person workbooks |
Real Excel formatting, not just values
- Merged cells: sort by one or more group fields (ascending/descending), then merge adjacent equal values — non-group columns never merge across group boundaries.
- Multi-level headers with horizontal and vertical merges, plus custom column groups.
- Number formats: currency (¥#,##0.00), percentage (0.0%), thousands separators and real date cells.
- Summary rows with sum / average / count / max / min chosen per column.
- Autofilter dropdowns, frozen header rows, themed header colors/fonts and full cell borders.
- Auto column width measured by content (double-width for CJK characters).
Excel/CSV → JSON reverse conversion
Drop a spreadsheet and the tool reconstructs JSON precisely: N-level merged headers become nested objects (user/name paths), merged data regions fill values into every covered row, duplicate labels get name_2 suffixes, and column types (number/currency/percent/date) are inferred from cell formats with majority voting — one click applies them as a custom header configuration.
Privacy and large files
- All parsing, merging and file generation happen in your browser — no uploads, no server, no registration.
- Workbooks with 5,000+ rows are generated in a background Web Worker with a progress bar, so the page stays responsive.
- CSV exports include a UTF-8 BOM (Excel opens Chinese correctly) and formula-injection guarding.
- Header configurations can be saved as local presets or shared via a self-contained URL — data is never included in the link.
Frequently asked questions
How is this different from the simple JSON to XLSX converter?
The simple converter is a fast batch file-in/file-out tool for plain tables. This studio is for presentation-ready output: multi-level headers, merged cells, nested-array strategies, summary rows, cell styles and seven export formats, with an editable preview before download.
Can nested JSON objects become two-row headers automatically?
Yes. Enable "Expand nested objects" in default mode (or use column groups in custom mode). Fields such as user.name and address.city produce merged parent headers with leaf columns underneath, using deep-path value extraction that also supports literal keys containing dots.
How are merged cells decided?
Rows are first sorted stably by the chosen group fields, then each column is scanned: adjacent equal non-empty values merge into one range. Columns you did not group only merge within the same group boundary, so two unrelated departments with the same value never collapse together.
What happens to arrays inside each record?
Three strategies: flatten them into multiple rows with parent-block merging, serialize the array as formatted JSON inside one auto-sized wrapped cell, or generate a main sheet plus one detail sheet per record.
Can I convert an Excel file back into nested JSON?
Yes. Merged multi-level headers are reconstructed back into nested objects, filled merged cells restore repeated values, and the header row can be specified manually when title rows exist. Cell number formats drive the inferred column types.
Does it work offline and is my data uploaded?
Nothing is uploaded. All processing happens locally in the browser tab; you can even disconnect after the page loads. Large jobs run in a Web Worker and presets live in your browser localStorage.
Related tools
Need a full spreadsheet editor with formulas, charts and pivot tables after converting? Open the free online workbook editor.
Open the XLSX editor