Online Tool Store
JSON Formatter
Format, validate, or minify JSON while preserving strings and number text exactly. Paste or upload a file, see clear syntax errors, then copy or download the result.
This works right here on your device — nothing gets sent out.
JSON workspace
Paste JSON below. Validation and every transformation stay in this browser tab.
Strict JSON only: property names need double quotes, and comments or trailing commas are invalid.
20 lines · 275 characters
How it works
- Paste JSON, upload a .json or .txt file, or start with the compact project sample already loaded above.
- The browser checks the complete document against strict JSON syntax and reports the error location when one is available.
- Pretty-print with 2 spaces, 4 spaces, or tabs; or minify the document to one compact line.
- Copy the result or download it as a ready-to-use .json file.
The formatting method
First, the browser's strict JSON parser verifies that the entire input is valid. The formatter then scans the original text character by character. It never changes anything inside a quoted string: escaped quotes, spaces, and Unicode escapes stay untouched.
Pretty-print = structural newlines + selected indentation Minify = remove whitespace outside quoted strings
Working from the validated source text instead of serializing a JavaScript object also preserves key order, duplicate keys, and long numeric literals exactly as written.
FAQ
Does the JSON I paste get uploaded or saved anywhere?
No. Validation, formatting, minification, copying, and file creation all happen inside your browser. Your JSON is never sent to Online Tool Store or any processing service.
Does formatting change JSON values or large numbers?
No. After validation, the formatter changes only insignificant whitespace outside quoted strings. It does not rebuild the document from JavaScript values, so number text, escape sequences, key order, and duplicate keys remain exactly as entered.
Why are comments, single quotes, or trailing commas rejected?
They are accepted by some JavaScript-like formats, but they are not part of the JSON standard. This validator uses strict JSON rules: property names and strings need double quotes, comments are not allowed, and the final item cannot have a trailing comma.
Can I format a top-level array, string, number, boolean, or null?
Yes. A valid JSON document can contain any JSON value at the top level, not only an object. Arrays, strings, numbers, true, false, and null are all supported.
How large can the JSON document be?
There is no artificial limit in this tool. The practical limit depends on your browser and available device memory; very large pasted documents can take longer to validate and display.
Can I upload a .json file instead of pasting?
Yes. Click "Upload file" and choose a .json or .txt file up to 10 MB. It is read directly in your browser with the File API and loaded into the input box — the file itself is never uploaded to a server.
How we compare
| Feature | Online Tool Store | JSONLint | CodeBeautify JSON Viewer |
|---|---|---|---|
| Works without installing a desktop app | Yes | Yes | Yes |
| Dedicated pretty-print and minify controls | Both, one click | Both, separate pages | Both, one click |
| Strict validation feedback with error location | Line and column, jump to error | Line number | Highlighted error |
| Preserves original long number text and key order | Yes — never re-serializes the value | Not guaranteed | Not guaranteed |
| Upload a local .json or .txt file | Yes | No, paste or URL only | Yes |
| Copy and download result | Both included | Manual copy | Both included |
| No account, ads-in-workspace, or upsells | Yes | No, ad-supported | No, ad-supported |
JSONLint and CodeBeautify add extra features like tree viewers and format converters, but route JSON through more surrounding UI and ads. For a fast, focused check that keeps your exact source text intact, Online Tool Store JSON Formatter is the simpler path — paste or upload, validate, transform, and copy without setup.