Convert Excel Spreadsheets to JSON Online Convert Excel spreadsheets (.xlsx, .xls) to JSON format with sheet selection.

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Excel to JSON

Convert Excel spreadsheets (.xlsx, .xls) to JSON format with sheet selection.

Upload Excel file

Drop or select your .xlsx, .xls, or .ods file.

Select sheet

Choose which sheet to convert if the workbook has multiple sheets.

Download JSON

Copy or download the JSON array output.

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What Is Excel to JSON?

Excel to JSON converts Microsoft Excel spreadsheets into JavaScript Object Notation format. Supporting .xlsx, .xls, .xlsb, and .ods file formats, this tool uses the SheetJS (xlsx) library for reliable spreadsheet parsing. The first row of each sheet is used as object keys, and each subsequent row becomes a JSON object. For workbooks with multiple sheets, you can select which sheet to convert. The conversion happens entirely in your browser — your spreadsheet files are never uploaded to any server.

Why Use Excel to JSON?

Supports .xlsx, .xls, .xlsb, and .ods file formats.
Multi-sheet workbooks supported with sheet selector.
Configurable JSON indentation (2 or 4 spaces).
Files never leave your browser — complete privacy.

Common Use Cases

API Development

Convert Excel data into JSON for use as API mock data or test fixtures.

Database Import

Transform spreadsheet data into JSON for import into MongoDB or other NoSQL databases.

Web Applications

Import Excel exports as JSON for frontend web applications.

Data Migration

Transform Excel-based data into JSON for modern data pipelines.

Technical Guide

File parsing is handled by the SheetJS (xlsx) library, which reads the uploaded file as an ArrayBuffer and parses the binary spreadsheet format. The library supports Microsoft Office formats (BIFF for .xls, OOXML for .xlsx), OpenDocument (.ods), and other spreadsheet formats.

The sheet_to_json() utility converts a worksheet into an array of objects using the first row as keys. Empty rows are typically excluded. Cell values are converted to their JavaScript equivalents: numbers, strings, dates, and booleans.

For multi-sheet workbooks, the SheetNames array provides the list of available sheets, and users can select which sheet to convert. The conversion processes only the selected sheet.

Performance note: Very large spreadsheets (100,000+ rows) may take several seconds to process in the browser. The xlsx library is optimized for browser use but memory usage scales with file size.

Tips & Best Practices

1
The first row of each sheet must contain column headers — they become JSON keys.
2
Merged cells may not convert as expected — unmerge cells before conversion.
3
Date cells are converted to JavaScript date representations — format as needed.
4
For large files, processing may take a few seconds depending on your device.

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Frequently Asked Questions

Q Which file formats are supported?

The converter supports .xlsx (Excel 2007+), .xls (Excel 97-2003), .xlsb (binary), and .ods (OpenDocument).

Q Is my file uploaded to a server?

No, all processing happens locally in your browser. Your file never leaves your device.

Q How are dates handled?

Excel date values are converted to JavaScript date representations. You may need to format them for your use case.

Q How are Excel formulas handled in the conversion?

Cell values are exported, not formulas. The computed result of each formula is included in the JSON.

Q Is there a file size limit?

The practical limit depends on your browser memory. Files up to 10-20MB typically process without issues.

About This Tool

Excel to JSON is a free online tool by FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration or installation required.