Excel to JSON Converter
Note: A spreadsheet stores dates as a day count from 1900, so a date column pasted as values arrives as five-digit integers. Turn on date conversion, or format the column as text before copying — otherwise the meaning is gone by the time it reaches here.
Type inference is where these conversions usually go wrong. "007" is a product code and must stay a string. "1,234.50" is a number in one locale and something else entirely in another. A leading apostrophe is Excel's marker for forced text and should not survive into the output. Dates are the worst case: a spreadsheet stores them as a serial number counting days from 1900, so a date column pasted as raw values arrives as five-digit integers. Each of these behaviours is a switch rather than a guess, so you can see what the tool decided and override it.
The two output shapes cover different consumers. An array of objects, keyed by the header row, is what an API or a JavaScript application wants. An array of arrays is more compact and preserves column order exactly, which matters when you are feeding a charting library or writing the data back to a grid.
Everything is parsed in the browser. No spreadsheet is uploaded, which is usually the point when the data is a customer list or a set of internal figures.
Frequently Asked Questions
Why did my dates turn into five-digit numbers?
Because that is how a spreadsheet actually stores them — as a count of days since 1900 — and pasting the raw values gives you the serial number rather than the display text. Enable date conversion to have those turned back into ISO dates, or format the column as text in the spreadsheet before copying.
My leading zeros disappeared. How do I keep them?
Turn off number inference, or turn on 'keep values with leading zeros as text'. A value like 007 or 01234 is nearly always an identifier — a product code, a postcode, a phone number — and converting it to a number destroys it irreversibly.
Can I upload an .xlsx file?
Not directly. An xlsx is a zip archive of XML, and parsing it properly needs a library large enough that loading it would slow the page for everyone. Copying the cells or saving as CSV takes a few seconds and keeps the tool light.
What happens to merged cells and formulas?
Formulas come through as their calculated values, which is what you want. Merged cells paste as the value in the first cell followed by empty ones, so a merged header spanning three columns produces one name and two blanks — worth checking before you convert.
