How do you convert Excel serial date numbers to ISO 8601 dates in JSON?

To convert an Excel date serial into an ISO 8601 UTC string, calculate UTC milliseconds using (serial - 25569) * 86400000 for 1900 date systems, accounting for Excel's historical leap year bug that counts non-existent February 29, 1900 (serial 60). In OpenXML workbooks (ECMA-376), cells with the 's' style attribute index into numFmts containing date patterns. Our client-side parser detects these style IDs, adjusts fractional day decimals into hours, minutes, and seconds, and serializes the result directly into an RFC 3339 / ISO 8601 timestamp (e.g., 2024-03-15T00:00:00.000Z).

What is the difference between Array of Objects and Column-Oriented JSON output?

Array of Objects formats tabular data row-by-row as [{'id': 1, 'status': 'active'}, {'id': 2, 'status': 'pending'}], whereas Column-Oriented JSON groups values by column key as {'id': [1, 2], 'status': ['active', 'pending']}. Array of Objects is standard for REST API payloads, MongoDB BSON documents, and ORM bulk inserts. Column-Oriented vectors eliminate repeating dictionary keys across thousands of records, reducing uncompressed JSON file size by 40% to 65% and optimizing memory throughput for columnar analytical engines like DuckDB, Apache Arrow, and frontend visualization libraries.

What is the maximum file size and row limit for client-side Excel to JSON conversion?

Client-side browser parsing safely handles XLSX workbooks up to 50 MB containing approximately 250,000 to 500,000 rows within 1.5 to 4 seconds, bounded only by the browser tab's V8 heap memory limit (typically 2 GB to 4 GB). Because file extraction is executed locally inside an isolated Web Worker using zero-copy ArrayBuffer streaming and O(N) linear single-pass parsing, zero byte data is transmitted across the network, ensuring strict compliance with GDPR, HIPAA, and SOC 2 confidential data processing standards.

Why does Excel convert 16-digit credit card or tracking numbers into scientific notation and how do you fix it?

Excel enforces the IEEE 754 double-precision floating-point standard, which supports only 53 bits of precision (representing 15 to 17 significant decimal digits, up to 9,007,199,254,740,991); any integer exceeding 15 digits has its trailing digits permanently rounded to zeros and displays as scientific notation (e.g., 1.23457E+15). To prevent precision loss during JSON export, format the column as 'Text' before input or activate 'Leading Zero Shield' so the converter extracts raw string tokens from the shared strings table (xl/sharedStrings.xml) instead of coercing through the numeric calculation pipeline.

How does the converter handle Excel formula cells versus calculated values?

The converter reads the cached formula evaluation stored in the OpenXML value tag rather than re-executing dynamic formula expressions in JavaScript. When an Excel workbook is saved, Microsoft Excel computes formulas (such as =SUM(A1:A50) or =XLOOKUP(...)) and serializes the resulting literal in the node adjacent to the formula definition. This guarantees 100% calculation parity with Excel's native formula engine without requiring external recalculation libraries.

How do you parse European Excel files that use comma decimals and semicolon delimiters?

European spreadsheets follow the DIN 5008 standard, utilizing semicolons (;) as list separators, commas (,) as decimal marks, and periods (.) as thousand groupings (e.g., 1.250,75 €). When parsing European CSV or XLSX exports, set the Decimal Separator to 'Comma (,)' and enable 'Number Sanitization', which swaps comma radix points to standard IEEE 754 period decimals and strips thousand-separator dots in a single regex sweep, preventing 1.250,75 from parsing as NaN or an inflated 125075.

Excel to JSON & XLSX Converter

Convert Excel to JSON instantly in your browser. Parse XLSX, XLS, and CSV files into clean JSON objects, nested trees, or column arrays with zero server upload.

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[
  {
    "sku": "004128",
    "product": {
      "title": "Aerodynamic Road Helmet",
      "category": "Cycling"
    },
    "pricing": {
      "retail": 129.99,
      "sale": 99.99
    },
    "inventory": {
      "stock": 42,
      "inStock": true
    }
  },
  {
    "sku": "004129",
    "product": {
      "title": "Carbon Fiber Bottle Cage",
      "category": "Accessories"
    },
    "pricing": {
      "retail": 34.5,
      "sale": 34.5
    },
    "inventory": {
      "stock": 115,
      "inStock": true
    }
  },
  {
    "sku": "007890",
    "product": {
      "title": "Thermal Winter Cycling Gloves",
      "category": "Apparel"
    },
    "pricing": {
      "retail": 49,
      "sale": 39
    },
    "inventory": {
      "stock": false,
      "inStock": false
    }
  }
]

Excel to JSON & XLSX Converter

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Excel to JSON & XLSX Converter Guide

Key Parameters & Controls

Pro Tips & Best Practices

Common Gotchas & Troubleshooting

⚠️Dates render as 5-digit integers (e.g., 45231) or timestamps show 4-hour timezone shifts in output JSON

⚠️Currency values with commas or parentheses parse as NaN or string primitives instead of numbers

⚠️Merged cell ranges cause downstream rows to populate with null or missing keys

Frequently Asked Questions

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