What Is a JSON Formatter and Validator?
JSON is the plain text format that APIs, apps, schema markup, Google Tag Manager and AI tools use to pass data around. It is easy for machines to read, but a single missing quote or extra comma breaks the whole thing, and long JSON on one line is almost impossible for people to read.
This tool does three jobs at once. It formats JSON with clean indentation, validates it against the official JSON standard (RFC 8259) and points to the exact line and column of any error, and repairs the most common problems, such as the broken JSON that ChatGPT and other AI tools often return. Everything runs in your browser, so private data never leaves your device.
How to Use the JSON Formatter
- Paste your JSON into the box. You can paste a whole AI answer, including the code fence and the text around it.
- Read the check. Green means valid. Red shows the line, column and a marker under the problem. Amber means the tool repaired it and lists every fix.
- Pick an indent of 2 spaces, 4 spaces or tabs, or choose Minify to put it all on one line for production.
- Tick Sort keys to order keys A to Z, which makes two versions easy to compare.
- Copy or download the result, or press Replace Input With Result to keep working on the fixed version.
Common JSON Errors and What the Tool Does
| Problem | Example | What happens |
|---|---|---|
| Trailing comma | {"a": 1,} | Flagged, then removed |
| Single or curly quotes | {'name': 'Tea'} | Changed to straight double quotes |
| Keys without quotes | {name: "Tea"} | Quotes added around the key |
| Python style values | True, False, None | Changed to true, false, null |
| Comments | // note or /* note */ | Removed, since JSON has no comments |
| Code fence and chat text | ```json with text around it | Only the JSON is kept |
| Missing bracket or quote | {"a": [1, 2} | Exact line and column shown so you can fix it |
| Duplicate keys | {"id": 1, "id": 2} | Warning, as most parsers keep only the last one |
Repairs never guess at your data. Numbers are kept exactly as written, so long IDs and prices do not lose digits the way they can in some online formatters.
Tips for Working With JSON
- Ask AI tools for JSON only. Add "Return only valid JSON, no extra text" to your prompt. If it still adds a comment or a trailing comma, paste it here.
- Minify for production, format for people. Minified JSON is smaller to send, while formatted JSON is easier to review in a pull request.
- Validate schema markup before testing it. A syntax error stops Google from reading your JSON LD at all, so fix syntax here first, then run Google's Rich Results Test.
- Save files as UTF 8. The standard requires it when JSON moves between systems, and it keeps accents and Indian scripts intact.
Put Your JSON to Work
Add structured data with how to add schema markup with JSON LD, push clean events with the GTM data layer explained, or return JSON from your own backend with a REST API in PHP without a framework. Need to send JSON inside a link? Encode it with the URL encoder and decoder.
Frequently Asked Questions
1Why is my JSON invalid when it looks fine?
The usual causes are a trailing comma after the last item, single or curly quotes, a missing comma between items, or an unescaped line break inside a string. The validator shows the exact line and column, with a marker under the character that breaks it.
2How do I fix broken JSON from ChatGPT?
Paste the whole answer here, including the code fence. The tool strips the text around it, removes comments and trailing commas, fixes quotes and Python style True, False and None, then shows valid JSON with a list of every change it made.
3Does formatting change my data?
No. Only spaces and line breaks change. Keys stay in the same order unless you tick Sort keys, and numbers are kept exactly as written, so long IDs keep every digit.
4Is it safe to paste private JSON here?
Yes. The formatter runs entirely in your browser. Nothing you paste is uploaded, logged or stored, so API responses, tokens and customer data stay on your device.