JSON Formatter and Validator
Make JSON easier to read, check its syntax or remove unnecessary whitespace. Your input stays in your browser.
- Free, no sign-up
- Text stays in your browser
- Paste code / no upload
Up to 500,000 character units. Input is not saved. Processing stays in this browser; pasted code is not executed.
Step by step
How to format and validate JSON
Step 1: Paste a JSON document into the input box, or load the example to try an API-style response. The input must use standard JSON syntax.
Step 2: Choose two spaces, four spaces or tabs, then select Format JSON. Use Validate JSON to check syntax, or Minify JSON for compact output.
Step 3: Review the output and byte counts. Copy the result or download a JSON file. Changing the input clears the previous output so you cannot accidentally copy an outdated result.
Readable JSON without changing number literals
Pretty printing adds indentation and line breaks around objects and arrays. It is useful when checking an API response, comparing configuration values or explaining a data structure to a colleague. Minification removes whitespace outside strings to create a compact version of the same document.
This formatter edits the source tokens rather than converting values into JavaScript numbers. Large integer IDs, decimal notation, escaped strings and key order are preserved. Duplicate keys also remain present: syntax validation does not prove that a document has unique keys or that your application will interpret it as intended.
Understand validation errors
JSON requires double quotes around property names and string values. Comments, trailing commas, undefined, NaN and JavaScript functions are not valid JSON. When validation fails, the tool reports the first detected error with a line and column. Fix that location and validate again; one missing delimiter can cause several later errors.
For example, the loaded response contains a name, an array of tool names and a boolean. Formatting expands the structure across lines; minifying returns a compact document. A top-level string, number, boolean or null is also valid JSON. This is syntax checking, not JSON Schema validation or an API contract test.
Local processing and output sizes
Input is processed in a browser worker and is not uploaded or executed. The editor accepts up to 500,000 UTF-16 units; some emoji use more than one unit. Oversized pastes may be truncated, so check the input before using a result. A processing timeout lets you retry with a smaller document.
Byte counts use UTF-8 encoding before gzip or Brotli compression. Formatted output can be larger than the input because indentation is added. The page reports either an increase or a reduction. Copy or download the result before navigating away because this editor does not save your draft.