json-formatter

Quick answer: Beautify or minify JSON and get exact syntax-error locations. Open json-formatter — everything runs locally in your browser, and files never leave your device.

Steps

1. Paste JSON into the JSON Formatter.
2. Choose indent (2/4 spaces) or minify.
3. Fix errors at the reported position, then copy the output.

Important notes

• Trailing commas and comments cause most failures — JSON has no comment syntax; strip them from config files first.
• Numbers beyond 2^53 lose precision — store long IDs as strings.
• Formatting reorders nothing; your data is untouched.

Common questions

Single-quoted keys? Invalid JSON — that is a JS object; convert quotes first.

Sort keys? Keep an editor plugin for that; this tool preserves order.

Workflow tips

When validating API responses, format the JSON and then collapse it again to compare payloads between environments — a minified diff of formatted-and-reminified output ignores whitespace noise and shows only real data differences.

Pro tips

Formatting JSON is also the moment to validate its shape, not just its syntax: paste, beautify, then scan the structure for the three silent killers — duplicate keys (last one wins silently in most parsers), inconsistent types across array items (a "price" that is "12.50" as a string in one object and 12.5 as a number elsewhere), and nulls where consumers expect objects. For config files, keep a formatted canonical version in version control and minify only at deploy time; debugging a minified config is misery you can prevent.

Why does my JSON parse here but fail in my app? Watch for a UTF-8 BOM at the file start and for trailing content after the closing brace — both are invisible here but fatal to strict parsers.