Good tools get out of your way.

One workspace for the whole document

Check syntax with the validator, make data readable with the formatter or beautifier, change the source in the editor, explore nested structures in the viewer, or remove whitespace with the minifier. They share the same document in your tab’s memory.

Preserve the details

Formatting should change whitespace, not values. This toolkit preserves number spellings, escaped strings, object member order, and duplicate keys. Duplicate keys generate an interoperability warning because other parsers may discard an earlier value.

Clear boundaries

Validation follows strict JSON syntax as described by RFC 8259. Comments, trailing commas, and JavaScript expressions are not accepted. The syntax validator does not repair input or check schemas. Dedicated tools provide Draft 7 schema checks, repair suggestions, comparisons, conversions, and JWT inspection.

The current limits are 10 MiB of UTF-8 input, 128 nesting levels, and a bounded tree preview of up to 2,000 nodes. Long values are shortened in the tree preview; formatted and downloaded output retain full values. Very large formatted output is stopped at 32 Mi characters. Device performance varies.

Made with open-source tools

The site uses Astro for static pages, CodeMirror for editing, and Microsoft’s jsonc-parser configured for strict JSON diagnostics. Formatting operates on the original source tokens. Heavy processing runs in a browser Web Worker.

Learn as you go

The JSON field guide explains common problems using examples you can open in the validator. For details about document handling and local preferences, read the privacy page.