JSON formatter, viewer, and validator

The right one is whichever handles your document without getting in the way. Worth checking before you settle on one: does it validate as well as indent, does it name the exact line and column when parsing fails, can it open a multi-megabyte file without freezing the tab, and does your data leave the browser? This page formats, validates, beautifies, and minifies JSON, then shows the result as a collapsible tree, a table, or indented text — with no account, no ads, and no upload, because every parse runs locally on your own machine.

A JSON formatter is a tool that parses a JSON document and writes it back out with consistent newlines and indentation, turning a single-line API response into something a person can read. Because it has to parse the input first, a formatter is also a validator — anything that will not parse stops with an error instead of being reformatted. Formatting only changes the whitespace between tokens, so your keys, values, types, and order come back exactly as they went in.

A formatter answers “how do I read this?” and a validator answers “is this correct?”. The same parse does both, which is why this page reports syntax errors while it formats. The separate JSON validator is for when checking is the whole job: it opens on the error panel and gives the line, the column, the offending source line with a caret under it, and a plain-language note about what the parser expected. Neither checks your document against a JSON Schema — that is a question about shape, not syntax.

Start at the reported position, because most failures are a single character. The usual culprits are a trailing comma before } or ], single quotes instead of double quotes, unquoted property names, // comments, and Python’s True/False/None — all legal in JavaScript or Python, none of them legal in JSON. Press Repair and each of those is rewritten, along with JSONP wrappers and newline-delimited records, so you can format the result straight away.

Paste the document and press Minify: whitespace between tokens is stripped and the size before and after is shown, so you can see what you actually saved. It pays off for payloads you are about to send over the wire or store, and costs you nothing to undo — Format reverses it exactly, byte for byte. The JSON minifier opens directly on that view.

Yes. The tree view expands and collapses any branch, and search walks the parsed data rather than the visible DOM, so a match buried inside a collapsed object is still found and the tree opens to reveal it. Every row copies its own value or the JSONPath that reaches it. Rows are built only when you open them and long arrays load in chunks, which is what keeps a big document responsive. The JSON viewer goes into more detail.

It is free, with no sign-in and no cap on how many documents you run through it. No extension is needed either — this is an ordinary web page, and because parsing happens in your browser rather than on a server it keeps working after you go offline. Alongside formatting there is a JSON beautifier for minified or escaped input and a JSON diff for comparing two documents by path.

No. The page calls the browser’s built-in JSON.parse, and file upload uses the local File API. There is no backend involved in formatting, validating, or viewing. You can disconnect from the network after the page loads and everything still works.

Nothing — they are three names for the same operation: re-serialising JSON with newlines and indentation so a human can read it. The output is byte-identical whichever page you start from.

Documents of several megabytes are comfortable. The tree only builds DOM for nodes you open, and arrays load 200 children at a time. Above roughly 1.5 MB the editor stops re-parsing on every keystroke and waits for you to press Format, so typing stays smooth.

The usual causes are a trailing comma before a closing bracket, single quotes instead of double quotes, unquoted property names, // comments, or Python’s True/False/None. All of these are valid JavaScript or Python but not valid JSON. Repair fixes each of them.

Validation uses the browser’s own parser, which implements RFC 8259 / ECMA-404. That is the same parser your application code will use, so a document that passes here will parse in production.

Yes. Sort keys orders object properties A→Z at every level of nesting. Array order is data rather than formatting, so it is left untouched.

Your most recent document (up to 500 KB), your indentation choice, your view preference, and your theme — all in localStorage on your own device, so a reload does not lose your work. Clear removes the document.

Paste the quoted string and press Unescape. A log line like "{\"id\":7}" becomes real JSON you can browse in the tree.