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JSON Formatter & Validator
Paste or upload JSON to check its syntax, format or minify it, and inspect nested data. Everything runs in your browser — nothing is uploaded.
Paste or upload JSON to check its syntax, format or minify it, and explore nested data in a readable tree. Everything runs in your browser — nothing you type or upload leaves your device.
0 B of 4.77 MB allowed
Your formatted result will appear here after you press Validate, Format, or Minify.
Paste JSON, load the sample, or choose a .json file to begin.
How to use this JSON formatter
Paste or upload JSON to check its syntax, format or minify it, and explore nested data in a readable tree. Everything runs in your browser — nothing you type or upload leaves your device.
How to use it: paste JSON into the input box, or choose a .json file (up to 5 MB). Press Validate to check syntax, Format to beautify it, or Minify to compress it. Read the result in the Code tab, or switch to the Tree tab to explore nested data, search, and copy values. Copy the output or download it as a .json file — your original input is never changed.
Validate, format, minify — what is the difference? Validate checks syntax and reports the first error in plain language, with its line and column. Format (beautify) rewrites valid JSON with consistent indentation so it is easy to read. Minify removes all unnecessary whitespace so the JSON is as small as possible for APIs and storage.
A quick invalid-to-valid example — JSON is strict: property names need double quotes and the last item takes no comma. Invalid { name: ‘Ada’, scores: [10, 20,] } versus valid { "name": "Ada", "scores": [10, 20] }.
Privacy and limits: parsing and formatting happen in a Web Worker inside this tab with a 5 MB limit (5,000,000 UTF-8 bytes) to keep the tool fast on phones and desktops. Oversized files are rejected before they are even read. Nothing is uploaded, stored, logged, or shared — closing the tab removes everything. Very large numbers (beyond about 15–16 digits) may lose precision when parsed, and duplicate keys keep only the last value.
FAQs
Why do trailing commas fail?
JSON follows RFC 8259, which does not allow a comma after the last item in an object or array. Remove it — or press “Apply fix” when the tool offers to remove trailing commas for you.
Must strings use double quotes?
Yes. JSON strings and property names must use double quotes. Single quotes, backticks, and bare words are not valid JSON, even if some programming languages accept them.
What about duplicate keys?
Duplicates are flagged as warnings, not errors: the last value wins, matching standard JSON parsing. Rename or remove the earlier key if it was unintentional.
Why is there a 5 MB limit?
Everything runs in your browser tab, so very large documents would slow down or crash the page. The 5 MB limit (5,000,000 UTF-8 bytes) keeps the tool fast on phones as well as desktops. Oversized files are rejected before they are even read.
Does my JSON leave my browser?
No. Parsing and formatting happen in a Web Worker inside this tab. Nothing is uploaded, stored, logged, or shared — closing the tab removes everything.
Runs entirely in your browser — nothing you type or upload leaves your device.