Checks JSON against RFC 8259 on every keystroke. A trailing comma in [1, 2, 3,] or a single-quoted key gets an exact line, column and caret plus a plain hint, so you can fix config files and API payloads before they fail in production.
How to use
- Paste JSON, drop a .json file or open one. It is validated as you type.
- If something is wrong you see the exact line and column, a caret under the problem and a plain explanation. Tap the error to jump there.
- Formatted view: choose 2 spaces, 4 spaces, Tab or Minify, and optionally sort keys. Copy or download the result.
- Tree view: expand and collapse nodes to explore. Tap a row to copy its path, such as $.items[3].name.
- CSV view: an array of objects becomes a table, with nested fields flattened into dot-notation columns. Download it for Excel or Google Sheets.
- Your JSON never leaves your browser. Files of 10 MB and more are fine.
- Numbers larger than JavaScript can represent keep their exact digits when formatting, where the browser supports it.
- Sorting keys is recursive and is handy before comparing two JSON files.
- CSV uses the first array of objects it finds. Arrays inside objects become numbered columns such as tags.0 and tags.1. The download includes a UTF-8 BOM so Excel shows accents correctly.
What makes JSON valid
JSON is defined by RFC 8259 and ECMA-404. Strings and keys must use double quotes, and only six value types exist: object, array, string, number, true/false and null. Comments, trailing commas, single quotes, NaN, Infinity and leading zeros such as 007 are not allowed, although JavaScript itself accepts several of them.
The usual errors are a comma after the last item, a missing comma between two items, an unescaped quote or line break inside a string, and a key without quotes. The validator names the problem and puts a caret under it, for example Unexpected token } at line 12, column 3 after a trailing comma.
Format, minify or sort
Beautifying adds indentation and line breaks so humans can read and diff the data; minifying removes every optional space, which typically saves 10 to 30 percent on indented files. Sorting keys recursively puts objects in alphabetical order, so two files with the same data but different key order compare cleanly. Very large integers such as 64-bit IDs keep their exact digits when formatting where your browser supports it.
Tree and CSV views
The tree lets you fold large documents and copy the path of any node in JSONPath style, such as $.items[3].name. The CSV view takes the first array of objects, uses the keys as column headers and flattens nested fields into dot notation like address.city, ready for Excel or Google Sheets.
Frequently asked questions
How do I find the error in my JSON?
Paste it and read the message under the editor: it gives the line, the column and a short explanation, with a caret under the exact character. Tap the message to jump there.
Does JSON allow comments or trailing commas?
No. Standard JSON (RFC 8259) has neither. Some tools accept JSONC or JSON5, but APIs and JSON.parse will reject them, so remove comments and trailing commas before sending data.
Is my JSON uploaded anywhere?
No. Parsing, formatting and conversion run in your browser, so you can paste API responses or config files with private data.
What is the difference between formatting and minifying?
Formatting adds indentation and line breaks for readability. Minifying removes all whitespace outside strings to make the file as small as possible. The data itself is the same.
Can I convert JSON to CSV here?
Yes. Switch to the CSV view: an array of objects becomes rows, keys become columns and nested fields become dot-notation columns. The download opens correctly in Excel.
Why are my big numbers changing in other tools?
JavaScript numbers are 64-bit floats, so integers above 9,007,199,254,740,991 lose precision when parsed. This formatter keeps the original digits when formatting where the browser allows; store such IDs as strings if you can.