JSON Formatter & Validator

Paste messy or minified JSON to get it cleanly indented — or minify it back to one line. Invalid JSON gets a clear error so you can find the problem fast. Everything runs locally in your browser.

How to use this calculator

Paste your JSON into the box.
Choose Beautify (with your preferred indent) or Minify.
Press Format. If the JSON is invalid, the error points you to the line and column.

Formula used

Parse → validate → re-serialize with chosen whitespace

The tool parses your input into a real data structure (catching any syntax error), then re-serializes it. That round-trip guarantees the output is valid and also normalizes it — consistent quoting, no trailing commas, standard escaping.

Example calculation

Worked example

Minified input {"name":"Nexify","active":true} beautifies to a clean two-line, indented object.

A stray trailing comma or single-quoted key triggers a precise error like "Invalid JSON (around line 3, column 12)" — turning a frustrating hunt into a direct fix.

Why a formatter earns its keep

JSON is strict where humans are loose: double quotes only, no trailing commas, no comments, no single quotes. Most "broken" JSON fails on exactly these, and API responses arrive minified into an unreadable wall. A formatter solves both — validating against the strict rules while pretty-printing the structure so you can actually read a nested payload.

The parse-and-reserialize approach is also a normalizer: it standardizes escaping and key quoting, so pasting hand-edited config through it produces canonical JSON you can trust. And because it runs locally, you can safely format responses containing tokens or private data.

Why use this calculator?

Turn minified API responses into readable, indented structures.
Validate JSON with error locations instead of a vague "parse failed".
Minify for production, or normalize hand-edited config to canonical form.

Frequently asked questions

Why is my JSON invalid?

The usual culprits: trailing commas after the last item, single quotes instead of double, unquoted keys, comments (JSON allows none), or a missing bracket. The error message here points to the line and column so you can spot it fast.

Does minifying JSON change the data?

No — it only removes whitespace between tokens. The parsed data is identical; the file is just smaller for transmission. Beautifying and minifying are lossless round-trips of each other.

Can JSON have comments?

Standard JSON cannot — that's a deliberate design choice. Variants like JSONC or JSON5 allow comments, but strict parsers (and this validator) reject them. For config files needing comments, use YAML or a commented superset.