Spreadsheet Converter

Overview

Convert spreadsheets between CSV, Excel (XLSX or XLS) and JSON, in any direction. The tool detects the CSV delimiter, so exports from other apps open without changing settings. A preview shows the result before you download. It all runs in your browser, so business data and personal records never leave your computer.

CSV to JSON for developersTurn a CSV export from a database, analytics tool or CRM into JSON that an API or app can read.
Excel to CSV for pipelinesStrip an XLSX file down to plain CSV for pandas, dbt or any command-line tool.
JSON to Excel for reportsTurn a JSON API response into an XLSX file for colleagues who work in Excel.
Sensitive recordsConvert payroll or compliance sheets without sending them anywhere, since nothing leaves the browser.
Fixing delimitersRe-save a semicolon-separated European CSV with commas, or as XLSX, before you merge it with other files.

Key features

CSV, XLSX en JSON in elke richting
Leest ook oude XLS-bestanden
Komma, puntkomma, tab of pipe als scheidingsteken
Live voorbeeld voordat je downloadt
Bestanden tot 50 MB
Herkent het CSV-scheidingsteken zelf

Set

Document 20

Neighbours

01 Factuur Generator 02 CSV naar JSON Converter 03 CSV naar XLSX Converter 04 E-mailviewer en -editor 05 EML naar MSG-converter 06 EML-viewer

Specification

Command: document.spreadsheet_converter
Set: Document
Input: MIXED
Output: MIXED
Max. bestand: 50MB
Batch: single file

CSV VND.OPENXMLFORMATS-OFFICEDOCUMENT.SPREADSHEETML.SHEET VND.MS-EXCEL JSON

Runtime

Engine: SheetJS · Intl.Segmenter
Threads: single
Isolated: —
WebGPU: —
Memory: —

Transport 0 B

Your file is opened, worked on and saved inside this tab. This tool has no upload step, so your file has nowhere else to go.

Keys

Zoeken: ⌘K
Panels: ⌘1 · ⌘2
Full width: F
All keys: ⌘/

How it works

Add your file

Drop in a CSV, XLSX, XLS or JSON file and the tool reads its format.

Pick the output

Choose CSV, XLSX or JSON, then set the delimiter, JSON shape or pretty printing if you need to.

Preview and download

Check the result in the preview, then download the new file.

Frequently asked

What file formats can I convert between?

CSV, Excel (XLSX and XLS) and JSON, in any direction. CSV to JSON, XLSX to CSV, JSON to XLSX and so on. Output is CSV, XLSX or JSON.

How does the tool handle different data structures?

Spreadsheet rows become a JSON list of objects, with the headers as keys. A JSON list of records becomes a table, with one column per key.

Can I customize the conversion options?

Yes. For a CSV you open, set the delimiter (comma, semicolon, tab or pipe), the decimal separator and the order of dates like 04/03/2026. For a CSV you create, pick its delimiter. For JSON, choose the shape (list of objects or list of arrays) and pretty or minified output.

What happens to complex data during conversion?

Excel formulas become their calculated values. Nested JSON objects become columns with dotted names, such as address.city, and lists are kept as JSON text in one cell.

Is there a preview before downloading?

Yes. The preview shows your data in the new format, so you can check it before you download.

Are there any file size limitations?

Files up to 50 MB work well. For bigger data sets, split the file first.

How is data privacy maintained?

Everything runs in your browser. Your files are never uploaded, so they stay on your computer.

Keys

Zoeken: ⌘K
Panels: ⌘1 · ⌘2
Full width: F
All keys: ⌘/