Free Online JSON Formatter
Format, validate, and minify JSON — right in your browser. No upload, no signup. Instant error detection with clear, helpful messages.
JSON Input
Output
How to Format JSON Online — Free & Private
Paste JSON
Paste your raw, minified, or messy JSON into the input box.
Format or Minify
Click Format to beautify with indentation, or Minify to compress to one line.
Copy Output
Review the result and copy it — all processing happens in your browser.
What is JSON Formatting?
JSON (JavaScript Object Notation) is the standard data format for APIs and config files. When sent between systems, it's usually minified — all whitespace stripped to save bytes — which makes it unreadable for humans. Formatting (also called beautifying or pretty-printing) adds line breaks and indentation so the structure is clear at a glance. Minifying does the reverse, removing all non-essential whitespace to produce the smallest possible valid JSON — useful before deploying or sending over the network.
Why Use Our Free JSON Formatter?
- 100% Private: Your JSON is parsed and re-serialized entirely in your browser. Nothing is uploaded to a server — safe for sensitive configs and API responses.
- Instant Validation: If your JSON has a syntax error, you get a clear message pointing to the problem — no more guessing where the missing comma is.
- Format & Minify: Beautify with 2 spaces, 4 spaces, or tabs. Or compress to a single line for production. One click each.
- Useful Stats: See the size, key count, and nesting depth of your JSON at a glance.
- Free Forever: No signup, no limits, no subscription. The tool is sustained through non-intrusive ads on the page.
Common JSON Errors (and How to Fix Them)
- Trailing comma:
{"a":1,}— remove the comma after the last item. JSON doesn't allow trailing commas. - Single quotes:
{'a':1}— JSON requires double quotes. Use{"a":1}. - Unquoted keys:
{a:1}— keys must be in double quotes:{"a":1}. - Comments:
// note— JSON has no comments. Remove them or use JSONC. - Special characters: Unescaped tabs or newlines in strings — escape them as
\tand\n.
Common Use Cases
- Reading API responses: Paste a minified API response to make it readable.
- Debugging: Spot structural mistakes in the JSON your code produces.
- Config files: Tidy up
tsconfig.json,package.json, or other JSON configs. - Preparing for deploy: Minify large JSON before shipping to reduce payload size.
- Learning: See how nested objects and arrays are structured.
Frequently Asked Questions
Is this JSON formatter really free?
Yes, completely free with no limits. We sustain the tool through non-intrusive advertising on the page.
Is my JSON uploaded to a server?
No. All parsing, formatting, and minifying happens locally in your browser using JavaScript. Your data never leaves your device.
Does it handle large JSON files?
Yes, it handles files of several megabytes. Since processing is in-browser, very large files may take a moment but work fine on modern devices.
Does it support JSONC or JSON5 (with comments)?
No — this tool follows strict JSON (RFC 8259). Comments, single quotes, and trailing commas will be flagged as errors. Strip them first if you need strict JSON output.
What indentation should I use?
2 spaces is the most common convention. 4 spaces is more readable for deeply nested data. Tabs are valid too — pick whichever your team prefers.
Can it fix my broken JSON automatically?
Not automatically — it tells you exactly what's wrong so you can fix it. Auto-repair risks silently changing your data's meaning, so we report errors precisely instead.
Does it work on mobile?
Yes! The formatter works on iOS, Android, and any modern mobile browser.