JSON → CSV converter

What happens to nested values and long numbers when JSON becomes CSV?

Open a developer’s JSON export or an API response in a text editor and all you get is braces, with no way to sort or total anything. This tool gathers the keys of an array of objects into column headers, lays each object out as one row and saves a CSV that opens straight in Excel. It flattens exactly one level deep, so it helps to know where nested values end up.

A closer look

Columns are built from every object’s keys in the order they first appear. A key that only shows up in a later object is added as a new column on the right, and objects without it leave that cell empty. When a value is itself an object or array, it is not split into columns; it goes into one cell as JSON text such as {"city":"Austin"}, with its inner double quotes doubled as CSV requires. An array of arrays becomes a table whose first array is the header, and an array of plain numbers or strings becomes a single column called value. A wrapper with exactly one key holding an array, like {"data":[...]}, is unwrapped automatically.

Strings are copied as written, so "00123" stays 00123; true and false become TRUE and FALSE, and null becomes an empty cell. Numbers are written out in full, never in scientific notation, so a millisecond timestamp such as 1719812345678 comes out as is rather than as 1.71981E+12. Whole numbers of 16 digits or more, such as long order numbers or IDs, are carried over as text before their last digits can be rounded, so they come out exactly as written in the JSON. The downloaded CSV carries a UTF-8 BOM so Excel reads accents correctly.

How to use it

• Choose a .json file in the Upload file tab, or put JSON in the Paste text tab and press Load as table. On this page, pasted text is always parsed as JSON.
• Check the preview header to see that every key became a column, and look for columns holding whole chunks of JSON text from nested values.
• Press Download CSV to save a .csv named after the original, or Copy result to take the text with you.

When it helps

Common snags

Tip Column order follows the key order of the first object, so if you want the columns in a particular order, arranging the keys of that first object is all it takes.