JSON formatter

Validate, format and minify JSON while preserving number and string tokens.

Check and format JSON

Validate strict JSON, find duplicate keys and format or minify a separate copy. Your file stays in this browser.

Choose a UTF-8 JSON fileOr paste JSON text

Input: up to 512 KiB, 128 nesting levels and 50,000 tokens. Output: up to 2 MiB. UTF-8 files only. A leading BOM is preserved in the download; some JSON consumers reject BOMs. Comments and trailing commas are rejected.

Only whitespace between tokens changes. Number spelling, negative zero, escapes, key order and duplicate keys are preserved. Duplicate keys remain ambiguous for other apps; this tool does not choose a winning value. Formatting uses LF line endings.

Output style

Choose a file or paste JSON, then press Check and convert.

Result preview

Shows at most the first 8,000 characters. The download contains the complete result. Pasted text is exported as UTF-8; earlier encoding or line-ending bytes cannot be recovered.

Inspect the JSON example without changing values

Try an example loads the sample and runs the 2-space formatter. Read the expanded object and items array in the preview; formatting changes only whitespace between tokens.
Check that id is still 900719925474099312345, value is still -0, and the message still contains the literal escape \u0026. The long number is not rounded, negative zero is not replaced with 0, and the escape is not rewritten as &.
The sample has two label entries in one object, so expect 1 duplicate occurrence warning. Both entries and their order remain. Decide which key and value you intended before using the JSON in another app; valid syntax does not resolve this ambiguity.

Choose Minify and run Check and convert to remove whitespace between tokens. The same number spellings, escape and both label entries remain. Download complete JSON for the full result; neither mode checks an API schema or chooses the correct value for your data.