JSON beautifier

Three kinds of unreadable JSON

“Beautify this” usually means one of three different problems, and each has its own button.

1. Valid but minified

One long line, no whitespace. Press Format. This is the easy case — the document parses, so it only needs re-serialising with indentation. Thetree viewer is often faster still, since it lets you open only the branch you care about.

2. Valid, but the JSON is inside a string

Log aggregators, message queues, and database TEXT columns commonly hand back a JSON document that has been encoded as a JSON string. It arrives dense with backslashes:

"{\"user\":{\"id\":41,\"tags\":[\"a\",\"b\"]}}"

Formatting this produces one very long string, because a string is genuinely all it is. PressUnescape instead: the outer string is parsed, the inner document is decoded, and you get real structure. Payloads encoded twice just need the button twice.

3. Not valid JSON at all

Snippets copied out of JavaScript source, Python REPL output, hand-edited config with comments, and JSONP responses are all near-JSON. Press Repair, then Format. What it handles:

• {name: "ada"} → property names get quoted
• {'name': 'ada'} → single quotes become double quotes
• [1, 2, 3, ] → the trailing comma is dropped
• // note and /* note */ → comments are stripped
• {"ok": True, "x": None} → Python literals become true and null
• {"n": NaN} → becomes null, since JSON cannot express NaN
• cb({"a":1}) → the JSONP wrapper is removed
• {"a":1}
{"a":2} → newline-delimited JSON is wrapped into an array

Repair puts its result in the editor rather than applying it invisibly, so you can read the diff before you trust it.

Sorting keys for comparison

Two documents that hold the same data in a different property order are tedious to diff.Sort keys orders every object A→Z at every depth, so beautify-then-sort both sides and a text diff shows only real differences. Array order is left alone — in an array, order is data rather than formatting.

Very large documents

Above roughly 1.5 MB the editor stops re-parsing on every keystroke and waits for you to press Format, which keeps typing and pasting smooth. Beautified output over 400 KB is shown without syntax colouring, because tokenising that much text costs more than the colour is worth; thetree stays fully interactive at any size.