JSON Formatter

Most of the JSON people paste into a formatter is not theirs to share: an API response with a customer's phone number, a config file with a database password, a webhook body with a payment ID. In November 2025 the security firm watchTowr reported that saved links on two popular online formatters exposed more than 80,000 pasted snippets, including passwords, cloud keys and personal data. This page has no save button and no share link. The text is read by code that runs in your tab, and nothing you paste is sent to TaskNinja or anyone else.

The error message is the part a validator is really for. Browsers word JSON.parse errors differently, and some only give a character offset. This page reads the text itself, so it can say there is a comma before } on line 3, column 12, or that a comma is missing at the end of the line above, or that a key needs double quotes. It points at the opening bracket when one is never closed, because that is the bracket you need to find, not the end of the file where the parser gave up.

Fix mistakes is for the JSON that is almost right. It removes // and /* */ comments and trailing commas, turns single quotes and the curly quotes that Word, Slack and phones insert into straight double quotes, puts quotes around bare keys, changes Python's True, False and None to true, false and null, changes NaN and Infinity to null, and adds a missing comma between items. Each change is counted in the result. It does not guess at missing brackets or cut-off text, because a repair that invents structure can quietly change your data.

Formatting here never changes a value. Numbers are copied exactly as written, so 1.10 stays 1.10 and a 20 digit order ID stays 20 digits. That matters because JavaScript stores numbers as 64-bit floats and rounds any integer above 9007199254740991: run 98234019283746501234 through JSON.parse and you get 98234019283746500000 back. When the page sees an integer that large it keeps it and warns you, so you can send it as a string instead. It also flags duplicate keys, which most programs silently resolve by keeping the last one.

Tree view is the quick way to understand a large response. Objects and arrays fold open one level at a time, long lists show the first 100 entries with a Show all button, and tapping a key shows its path, such as $.items[0].sku, ready to copy into code or a jq filter. JSON Lines files, with one record per line as used by logs and data exports, are detected automatically and each record is checked on its own.

The page never uploads your text or file. Formatting, validation and repair run in JavaScript in this tab, and the result exists only in this tab and in what you copy or download. Analytics counts anonymous events such as the tool being opened or a result being copied, never the JSON, its size in exact bytes, or a file name. Ads on the page do not see what you paste.

Even so, treat real secrets with care. If you pasted a live API key or password to read a response, rotate it if it was ever shared somewhere it should not have been. A private formatter keeps this page from leaking it; it cannot undo a leak that already happened elsewhere.