FREEFILEKIT FILE GUIDE

Convert CSV and JSON without losing leading zeros

Customer numbers, postal codes and product identifiers often look like numbers but need to remain text. An identifier such as 0012 is different from the number 12. Choose a conversion workflow that preserves that distinction.

CSV to JSON keeps field values as strings

Paste a table with a header row into CSV to JSON. Choose comma, semicolon or tab as the separator. The first row becomes the object keys; each following row becomes one object. Headers must be non-empty and unique.

name,id
Ada,0012

The identifier in the JSON result is "0012", including its leading zeros. Field values are not automatically converted into numbers, dates or booleans.

Quotes protect commas and line breaks

A field containing a comma can be written as "Ada, L". A quote inside a quoted field is written twice: "She said ""hello""". Quoted multiline fields are supported. Every data row must have the same number of fields as the header; a mismatched row produces an error rather than a silently shifted table.

Use strings for large JSON identifiers

Before using JSON to CSV, make identifiers JSON strings, such as "9007199254740993". The tools reject unsafe integer values instead of silently rounding them. JSON-to-CSV accepts an array of flat objects; nested objects and arrays must be flattened first. Missing keys and null values become empty CSV cells, so that distinction cannot be recovered from the CSV alone.

Check spreadsheet import settings

A CSV can preserve 0012, but a spreadsheet may still interpret it as a number when opening the file. Import identifier columns as text in your spreadsheet application. Format conversion cannot control the settings of the application that reads the result.

Formula protection and limits

JSON-to-CSV enables spreadsheet formula protection by default: formula-like text receives an apostrophe prefix. Leave it enabled for untrusted data; disable it only when exact strings are necessary and you understand how the destination handles formulas. Inputs are limited to 5 MiB, output to 20 MiB, and CSV tables to 50,000 rows, 1,000 columns and 500,000 cells. The preview can be shortened while the download contains the complete accepted result.