JSON Formatter & Validator

No. Formatting, validation and every conversion run in your browser, and nothing is sent to a server. That makes it safe to paste API responses, config files and test data. The page does not save your input either: close the tab and it is gone.

Look at the line and column shown under the input and press Go to error. The most common causes are a trailing comma after the last item, single quotes instead of double quotes, a key without quotes, a missing comma between two items, or a comment. When the page can repair the text safely, a Try to fix automatically button appears, and an Undo button brings your original back.

It accepts text that is almost JSON and rewrites it as strict JSON: it removes comments and trailing commas, turns single-quoted strings and unquoted keys into double-quoted ones, adds missing commas between items, changes Python True, False and None to true, false and null, and closes brackets that were left open when the text was cut off. It lists exactly what it changed. It cannot guess missing data, so always read the result.

No. Numbers are kept exactly as you wrote them, so a 20-digit ID is not rounded the way JavaScript’s JSON.parse would round it, and 1.0 stays 1.0. Keys stay in their original order, including keys that look like numbers. If you tick Sort keys, the output is ordered A to Z instead.

JSON is stricter than JavaScript. Keys and strings need double quotes, there are no comments, no trailing commas, no undefined, NaN or Infinity, and numbers cannot start with a plus sign, a dot or a leading zero. A line break inside a string must be written as \n. The message points at the first place that breaks a rule.

JSON technically allows the same key twice in one object, but most programs silently keep only the last value. The page warns you with the line number so you can decide which one you meant. Nothing is removed for you.

A list of objects becomes a table: each object is a row and each key is a column. Nested objects are flattened into columns such as address.city. A list inside a row is kept as JSON text in one cell, because there is no single right way to spread it across columns. You can pick comma, semicolon or tab as the separator.

It is a good starting point rather than a guarantee. Types are guessed from the one example you paste, so a key that is missing from some items is marked optional, and a value that is sometimes a string and sometimes null becomes string | null. If your data has rare shapes that are not in the sample, add them to the interface by hand.

JSONPath is a small query language for picking values out of JSON. Start with $ for the root, then use dots for keys, [0] for a list position, [*] for every item, .. to search at any depth, and filters such as [?(@.price<10)]. In the Find tab you can also just type a word to see every key or value that contains it, with a copyable path for each one.

You can open a file up to 20 MB. A few megabytes work smoothly because the tree only draws the branches you open and long lists are shown 200 items at a time. Very large files depend on your device’s memory, and syntax colouring is switched off for very large results to keep the page responsive.

Yes. If the text is not one JSON value but every non-empty line is valid JSON, the page reads it as JSON Lines and shows it as a list. You can then format it, browse it or convert it to CSV.

Strict validation follows the official JSON rules, so comments and trailing commas are reported as errors. The Try to fix button understands the common JSON5 and JSONC habits (comments, trailing commas, single quotes, unquoted keys) and converts them to standard JSON, but it is not a full JSON5 parser.