JSON Formatter & Validator (Free, No Login)
Format, minify, and validate JSON directly in your browser. Paste JSON, choose Format for two-space indentation or Minify to remove whitespace, and read a clear error with line and column when the input is invalid. Copy the result or download it as a .json file. Nothing is uploaded; no login or API key is needed.
Parsing and formatting use your browser's built-in JSON engine. Large documents run on the main thread and may be slow.
How to format and validate JSON without uploading it
Paste JSON into the input box and press Format to rewrite it with two-space indentation. The output keeps arrays and objects on separate lines, which makes nested API responses and configuration files much easier to read. Press Minify to remove optional whitespace when you need a compact string for a request body or an environment variable. Press Validate when you only want a yes-or-no check and do not need to change the text. Copy sends the current result to your clipboard, and Download saves it as formatted.json.
When the input is invalid, the tool shows the browser's error message and, when the message includes a character position, converts it to a line and column. That position points at the character where parsing stopped, which is usually near the real mistake but can be slightly after it. Common causes are a missing comma, a trailing comma before a closing bracket, single quotes instead of double quotes, an unquoted key, or a comment. Standard JSON has no comments, so remove them before validating.
Formatting is not lossless for every possible input. The browser parses the text into a JavaScript value and then serializes it again. Duplicate object keys collapse to the last value, integers larger than about 9 quadrillion lose precision, and numbers such as 1e3 are written as 1000. Object key order is generally preserved, but you should not rely on it. Use this tool for inspection and cleanup, not as a byte-for-byte formatter.
Everything runs locally, so secrets in the JSON stay in the tab. There is no fixed byte limit in the code, but very large files can freeze the page because parsing happens on the main thread. If a document is several megabytes, split it or use a desktop editor. For converting between CSV and JSON, use the CSV/JSON converter; for comparing two formatted documents, use the diff tool.
FAQ
Is this JSON formatter free and private?
Yes. The page runs entirely in your browser with no signup, no account, and no payment. Your JSON is parsed locally by your browser and is never uploaded to a server.
What is the difference between format and minify?
Format rewrites the JSON with two-space indentation and line breaks so it is easier to read. Minify removes every optional space and line break to produce the smallest valid representation.
Why does the validator show a line and column?
When the browser reports a character position for a syntax error, the tool converts that position into a line and column so you can find the problem quickly. Some browser messages do not include a position, in which case only the error text is shown.
Can it fix invalid JSON or understand comments?
No. It reports errors but does not repair them, and standard JSON does not allow comments or trailing commas. Remove comments and trailing commas before validating.
Does formatting change my data?
The values and structure stay the same, but the text can change in harmless ways. Duplicate object keys are collapsed, very large integers can lose precision, and numbers such as 1e3 are written as 1000 because the browser parses and re-serializes the JSON.
Is there a size limit?
There is no fixed limit in the code, but very large documents can make the tab slow or unresponsive because parsing and re-serializing happen on the main thread. For multi-megabyte files, use a desktop JSON tool.