Everyone has lost an afternoon to a stray trailing comma in a JSON file. The fix isn't "be more careful" — it's automating validation at every step: in your editor (pre-commit hooks), in CI, and — when nothing else is handy — in an online formatter that validates as you type.
The typical flow
- Paste the API response into the JSON formatter.
- Hit "Validate": it tells you if the document is correct, and if not, the exact line and column of the error.
- Use "Format" to indent it at 2 or 4 spaces.
- When shipping something to a production
.jsonfile, use "Minify" to strip whitespace and save bytes.
Minifying: how much you actually save
Whitespace, tabs and line breaks typically account for 15–30% of a JSON file's weight. The formatter shows you the bytes saved on every minification. For even more, combine minification with short, non-inflated key names.
Common errors and what they look like
- Trailing comma after the last element — the classic Git-diff offender.
- Single quotes — JSON doesn't accept them; error #2 on the list.
- Leading zeros in numbers —
01isn't valid JSON. - Trailing decimal points — neither is
1.
JSON ↔ CSV ↔ YAML
From the same editor you can also convert in both directions: JSON to CSV (array of objects → table) and JSON to YAML (for Docker Compose, Ansible or Kubernetes configs). Each tool respects the target syntax and warns you if something isn't convertible.
When the JSON is large: tree view, Schema and types
A deeply nested JSON document with hundreds of lines is hard to read as plain text. The tree viewer renders it as a collapsible structure so you can jump straight to the key you're after, no endless scrolling.
If the JSON is an API response you're about to consume in TypeScript, don't hand-write the type: paste it into the TypeScript converter and get the interface generated automatically, with nested types resolved. And if you need to document or validate the shape of the document — for an API contract, say — the JSON Schema generator builds the $schema from a real example.
The golden rule: validate before you save, minify before you ship.