JSON Formatter, Validator and Converter
Format, minify and deep-sort keys, with syntax errors located by line and column — then convert to YAML or a TypeScript type. Nothing leaves this page.
—Nothing leaves this page — the site is static assets with no backend that could receive it.
The YAML direction is one-way on purpose: writing JSON as YAML is a closed problem, parsing arbitrary YAML back is not.
What is different here
Validation runs as you type; formatting is a button, because reflowing text under the caret moves it. Errors land on a line and column where that is possible: V8 usually supplies them and they are passed through; a bare character offset ("position 3184" tells you nothing about a minified payload) is converted; and for the message shape that reports only a snippet, the character is located only when it appears exactly once — guessing between candidates would be worse than saying nothing.
Sort keys is a deep sort, and its purpose is not tidiness: it makes two dumps of the same object
diff cleanly. Two JSON files with the same content in a different key order show up in
git diff as a wholesale rewrite.
The two conversions exist for what people do next after formatting.
To YAML for moving a config between formats;
to a TypeScript type for anyone about to consume the payload in
code. Arrays become a union of their element shapes, and a null yields
unknown | null — a null in the sample says the field is nullable, not
that its type is null.
YAML is one-way on purpose. Writing JSON as YAML is a closed problem; parsing arbitrary YAML back (anchors, aliases, multi-document streams, implicit typing) is not, and a half-working importer is worse than none. For the same reason there is no parsing library here: a 40 KB dependency is not worth making every visitor download.