What this does

A reply comes back from someone else's API as one line three screens long, and there is a mistake somewhere in it. JSON Tools lays that line out with indentation, tells you the line and column where the parser gave up, squeezes it back down when you need it small again, and turns an array of objects into CSV. All of it happens in your browser.

There is no account, no upload and no server to sign in to. The page loads its own script and stylesheet and then talks to nothing else — what you paste is parsed by the browser's own JSON.parse and never leaves the tab. That also means it keeps working offline once the page is open.

The five tabs

• Formatter — re-indents with 2 spaces, 4 spaces or 8, and copies the result to the clipboard in one press.
• Validator — says whether the text parses. When it does not, it repeats the parser's own message and converts its character offset into a line and column you can jump to in your editor.
• Minifier — takes formatted JSON and strips every space and newline back out.
• JSON → CSV — takes an array of objects, uses the union of all their keys as the header row, and leaves a cell empty where an object has no such key. Values containing a comma, a quote or a newline get quoted and their quotes doubled; a nested object or array is written into its cell as JSON. Copy it, or download a .csv.
• Tree view — walks the whole structure as a collapsible tree, labelling every node object, array, string, number, boolean or null.

What JSON → CSV does with missing keys

Paste this:

[{"name":"Alice","age":25},{"name":"Bob","city":"Berlin"}]

and you get this:

name,age,city
Alice,25,
Bob,,Berlin

Both objects contribute their keys to the header, and neither row invents a value it does not have. Keys are collected from the top level of each object only — this is a flattener for table-shaped data, not a general nested-to-columns converter.

Who it is for

Anyone reading someone else's API response: a developer debugging an integration, a support engineer pasting a log line out of a ticket, an analyst who was handed a JSON export and wants it in a spreadsheet. It assumes you can read JSON — it does not explain the format, it just makes an unreadable blob readable.