Tech Tips

How to Format & Validate JSON Online (Free Developer Tool)

API responses come minified, config files come with 400 lines on one row, and one missing comma breaks everything. Here's the fastest way to format and validate JSON.

The 5-second method

1. Open [JSON Formatter](/developer-tools/json-formatter)

2. Paste your JSON

3. Pick indent (2 spaces, 4 spaces, or tab)

4. Copy the pretty-printed result — or spot the error line if invalid

Runs in your browser. Nothing uploads.

What it does

• Pretty-print — expand a one-line blob into readable indented JSON
• Minify — collapse pretty JSON into one line for production
• Validate — show the exact line + column of a syntax error

Common JSON errors

• Trailing comma — JSON doesn't allow `,` before `]` or `}`
• Single quotes — JSON needs double quotes for both keys and strings
• Unescaped characters — inline double quotes need escaping
• `undefined` values — JSON has `null`, not `undefined`
• JavaScript comments — invalid in JSON

The formatter highlights the exact spot the parser bailed.

Related tools

• [Base64 Encode / Decode](/developer-tools/base64-encode)
• [URL Encode](/developer-tools/url-encode)
• [Hash Generator](/developer-tools/hash)
• [Regex Tester](/developer-tools/regex-tester)

Pro tips

• Sort keys alphabetically for stable git diffs
• Two-space indent for web configs, four-space for docs
• Minify before pasting into environment variables
• Never paste production secrets into any online tool

Try [JSON Formatter](/developer-tools/json-formatter) — free, no signup, private.

4 min read