About JSON Prettify Formatter

A JSON formatter turns minified, messy, or log-copied JSON into a readable nested structure and helps point you to the line that breaks parsing.

This tool formats, minifies, validates, and lets you inspect JSON as a tree directly in your browser, which is useful for API responses, config files, and debugging payloads.

How to use the JSON Formatter

Paste JSON into the input area, or load the sample to check the expected output shape.
Click Format to pretty-print a one-line payload, or Minify to remove whitespace for transport.
If parsing fails, start with the reported line and column, then check commas, quotes, and matching brackets.
Copy the result when it looks right, or switch to the tree view to inspect deeply nested fields.

When you would use it

Expand a one-line API response while debugging backend or frontend integration.
Check package.json, manifest files, or mock payloads for trailing commas before committing them.
Minify a request body into one line without accidentally changing string content by hand.
Format escaped JSON from production logs, then compare it with another response in Text Diff.

JSON syntax and common errors

Standard JSON allows objects, arrays, double-quoted strings, numbers, booleans, and null. Most failures come from JavaScript-like syntax that JSON deliberately does not allow.

Trailing comma: the final item in an object or array cannot have an extra comma.
Single quotes: JSON strings and keys must use double quotes.
Unquoted keys: {name:"dev"} is a JavaScript object literal, not JSON.
Comments: standard JSON does not support // or /* */ comments; remove them or use JSON5.

JSON Formatter FAQ

Is my JSON uploaded anywhere?: No. Formatting, minifying, validation, and tree browsing run locally in your browser; content is not uploaded to wetool.site.
What is the difference between Format and Minify?: Format adds indentation and line breaks for reading. Minify removes unnecessary whitespace for transport or single-line config fields.
Why does it say my JSON is invalid?: The usual causes are a trailing comma, single quotes, an unquoted key, mismatched brackets, or extra log text copied with the JSON.
Can it handle large JSON?: Yes. Heavier parsing work is kept in a Web Worker where possible so large payloads do not freeze the main interface.
Does it support JSON5 or comments?: This formatter validates standard JSON. Convert JSON5 features such as comments, single quotes, or trailing commas before parsing.

Why use a browser-based JSON Formatter

JSON often contains internal API data, tokens, logs, or user records. Local browser processing reduces the risk of pasting sensitive payloads into a third-party server and still works when the network is unreliable.

Strict JSON vs JSON5 migration checklist

Many “JSON prettify failed” inputs are actually JavaScript objects or JSON5. Production APIs, config files, and log fields usually still expect strict JSON.

Change single-quoted strings to double quotes, and quote every object key.
Remove trailing commas, // comments, and /* */ comments before using a strict JSON parser.
NaN, Infinity, undefined, Date objects, and functions are not valid JSON values; convert them to strings, numbers, booleans, null, arrays, or objects first.

Large JSON debugging checklist

Large API responses and log payloads need more than prettify: you also want to avoid browser freezes and accidental data edits.

Format first, then search for field names; this is more reliable than searching nested paths inside one-line JSON.
Before comparing two responses, format both with the same indentation so the diff is not dominated by whitespace or minified structure.
If JSON came from logs, remove timestamps, log levels, escaping wrappers, and surrounding text so only the real JSON fragment remains.