A private alternative to JSONLint and JSONFormatter.org

What these sites offer today

JSONLint, on its public page, offers validation (paste JSON or enter a URL, with errors reported with line numbers), formatting, a minify option and a JSON diff. It also lists converters to and from CSV, Excel, SQL, YAML, XML and code languages, a JSONPath query tool, a schema validator and generator, a tree viewer, a JWT decoder and a repair tool. It points to an open-source npm package that powers its validator. Its page does not say whether validation runs in the browser or on a server, and loading JSON from a URL implies the site fetches that URL on your behalf.

JSONFormatter.org describes formatting with two, three or four spaces of indentation, minifying, validation with line-numbered errors, an optional fixer for some mistakes such as missing quotes, a tree view and a graph view, converters to XML, CSV and YAML, file upload and download, and loading from a URL. It saves the last JSON you formatted in your browser's local storage, and offers an online saving feature where you can add a title and choose an expiry; some expiry options require login, and links saved without logging in are public.

Both are capable and widely used. The differences that matter are about where your data goes and which extra tools you need, not about the quality of basic formatting.

Comparison

Based on each site's public description and how our tool is built; these sites change, so check the current version.

Why where the data goes matters for JSON

People paste surprisingly sensitive JSON into formatters: API responses with tokens, customer records, configuration files with connection strings, logs with email addresses. Most of the time that is fine on a tool that runs locally. It is a different risk calculation on a site that stores or shares data, or whose processing location is unclear.

A formatter that runs in your browser sidesteps the question. Your text is parsed with the browser's own JSON engine and re-printed with indentation you choose. No request is made, which you can confirm in the network tab, or by working offline after the page has loaded.

For anything containing tokens, keys or personal data, prefer a tool that processes locally and stores nothing.

How to format and debug JSON with our tool

The aim is to get from a broken blob to something readable quickly.

1. Open JSON Formatter and paste your text. Choose your indentation or switch to minify.
2. If the JSON is invalid, read the error. It names the line and column where parsing failed, which is usually just after the real mistake.
3. Check the usual suspects: a trailing comma after the last item, single quotes instead of double quotes, unquoted keys, comments (which JSON does not allow), a missing closing bracket, or an unescaped quote or newline inside a string.
4. Fix the text and re-run. When it parses, copy or download the formatted result.
5. To compare two versions of a payload, use JSON Diff, which compares structure instead of raw text.

Examples of common errors

Strict JSON is less forgiving than JavaScript object literals, which is why code that "looks right" often fails validation.

• Trailing comma: {"a": 1, "b": 2,} is invalid. Remove the final comma.
• Single quotes: {'a': 1} is invalid. JSON requires double quotes for keys and strings.
• Unquoted key: {a: 1} is invalid in JSON, although it is a valid JavaScript object.
• Comments: // and /* */ are not part of the standard. Remove them or use a different config format.
• Special numbers: NaN, Infinity and leading zeros such as 007 are not valid JSON numbers.
• Raw newlines inside strings must be written as \n.

Related tools for the next step

After formatting, people usually want to transform the data. On this site, JSON to CSV flattens arrays of objects for a spreadsheet, and CSV to JSON does the reverse. JSON to YAML and YAML to JSON help with configuration files, JSON to XML and XML to JSON help with older systems, and JSON to TypeScript generates interface types from a sample. JSONPath Tester lets you try expressions against your data, and JSON Diff highlights what changed between two versions.

Each is a separate tool, which keeps every page quick and focused instead of one crowded screen.

When another tool is the better choice

An established site or other software is the better pick when:

• You want to load JSON by pasting a URL and have the site fetch it for you.
• You want a shareable link to a formatted document. We store nothing, so we cannot provide links.
• You want automatic repair of broken JSON, a graph view, or a rich tree explorer for deep structures.
• You need validation against a JSON Schema as a built-in feature.
• You work with huge files of hundreds of megabytes. An editor such as VS Code, or command-line tools such as jq, handle those better than a browser tab.
• You need formatting inside your editor or in an automated build; use an editor extension or a library such as the open-source package JSONLint points to.

Limits of our formatter

It validates strict JSON only. It does not repair, accept comments, or understand JSON5 or JSON Lines as one document. Very large inputs depend on your browser memory, and pretty-printing can make the output many times larger than minified text. Also note that JSON.parse-style engines represent very large integers as floating-point numbers, so numbers beyond about 15 to 16 digits can lose precision; keep such IDs as strings.

Frequently asked questions

Try these tools