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JSON formatter & validator
Format, beautify, validate and minify JSON instantly. Pinpoints syntax errors by line and column. Private — runs in your browser.
🔒 Runs 100% in your browser — safe for real dataHow to use the jSON formatter & validator
- Paste JSON into the left box.
- Choose Format or Minify, indentation and key sorting.
- Copy the result — errors are shown below the boxes.
About this tool
Paste minified or messy JSON to pretty-print it with your chosen indentation, or minify it to the smallest size for APIs and config files. If the JSON is invalid, the validator reports the error and its line and column so you can fix trailing commas, missing quotes or unescaped characters.
FAQ
Is my data sent to a server?
No. DevKnife tools run entirely in your browser with JavaScript. Nothing you paste — API keys, tokens, customer data — is transmitted or logged, so it is safe for production data.
What are the most common JSON errors?
Trailing commas after the last item, single quotes instead of double quotes, unquoted keys, comments (not allowed in JSON) and unescaped line breaks inside strings.
Is there a size limit?
Only your browser’s memory — multi-megabyte files format in well under a second.
Related tools
Working with spreadsheets?
After converting JSON to CSV, try our ready-made Excel & Google Sheets templates — or the free ones.