How do I format minified JSON online?

Paste or open your JSON and it is formatted as you type. The Formatted tab shows indented output, and errors are pinpointed to the exact line and column.

Does formatting JSON change the data?

No. Formatting changes only whitespace and indentation. Values and structure are untouched, and long numeric ids keep every digit.

Why is my JSON invalid?

Common causes are missing or trailing commas, unmatched brackets, unescaped quotes, comments, and strings using single quotes. Forgiving mode accepts these and Tidy in place rewrites them as strict JSON.

Can I convert JSON to Excel or CSV?

Yes. The Table tab turns the largest array of objects into a spreadsheet, with a choice of separator, and writes a real .xlsx file in the browser.

Is it safe to paste private JSON here?

Yes. Parsing, formatting and exporting all happen locally in your browser. QuickDeveloperTools never uploads or stores the JSON you paste or open.

Are duplicate keys detected?

Yes. Standard parsers silently keep the last value; this one reports duplicate keys with both line numbers so you can decide what was intended.

Format · Validate · Convert · Free forever

JSON readable

Paste it once and take it anywhere — formatted, minified, as a browsable tree, an HTML table, a CSV, or a real Excel file. Broken JSON is pinpointed to the exact line and column with a plain-language fix.

📥 Reads 4 formats

JSON · NDJSON · JS objects · JSONC

📤 Writes 5 files

.json · .html · .csv · .tsv · .xlsx

🩹 Checks on every parse

Line & column · duplicate keys · big integers

⚡ Handles no upload

20 MB files · 50k rows · streams without freezing

Nothing is uploaded and nothing is saved. Parsing happens inside this browser tab — close it and your data is gone. Safe for keys, invoices and customer records.

No account · No upload · No trace

Step 1

Your JSON

empty

Parsing

drop a .json file to load it

Step 2

Output

Indent

the bars show nesting depth per line

waiting for valid JSON

—

Nothing to check yet Paste or open a file to begin.

Worth knowing

Long numbers survive the trip

A 19-digit id like 7203541998320016412 loses its last digits the moment it becomes a JavaScript number. This page keeps the original digits in every output and flags the ones at risk.

Duplicate keys are reported, not swallowed

Standard parsers keep the last value and say nothing. If the same key appears twice in one object, you get a warning with both line numbers.

Forgiving mode for real-world text

Turn it on to accept // and /* */ comments, trailing commas, single quotes, unquoted keys, and one JSON object per line. Tidy in place then rewrites it as strict JSON.

How the spreadsheet is built

The largest array of objects becomes the sheet. Nested objects turn into dotted columns like customer.city, lists of plain values are joined with commas, and anything deeper is kept as JSON text. Pick a different array from the dropdown at any time.

Excel files are written here, not fetched

The .xlsx is assembled in the page: a bold frozen header row, filters, and sized columns. Numbers stay numbers, and huge ids stay text so Excel cannot round them off.

Works offline

Once the page has loaded there are no further requests. Large files stay on your machine, which also means very large documents are limited by your own memory rather than an upload cap.

Other tools

XML Formatter Format and inspect XML the same way. JWT decoder Read the header and payload of a token. Base64 Encoder Encode or decode Base64 strings. Images to PDF Combine images into one document.

FAQ

Common questions

How do I format minified JSON?

Paste it, or open a file. Formatting happens as you type - there is no button to press. Errors are pinpointed to the line and column.

Does formatting change the data?

No. Only whitespace changes. Long numeric ids keep every digit, which is not true of most formatters.

Is my JSON uploaded?

No. Parsing, exporting and the Excel file are all produced in your browser. Nothing leaves the page.