JSON Formatter & Validator
Paste or open JSON to validate its syntax, format it for readability, or minify it locally in your browser.
Private, browser-local processingYour JSON is processed locally in your browser and is not uploaded to Savezly.
What JSON Formatting Does
Formatting adds consistent whitespace without changing valid token lexemes.
Validate Strict JSON Syntax
Validation checks strict JSON syntax, not JSON Schema or business rules.
Objects, Arrays, and Primitive Roots
Objects, arrays, strings, numbers, true, false, and null are valid root values.
Formatting Versus Minifying
Formatting improves readability; minifying removes insignificant JSON whitespace.
Understanding Syntax Errors
Invalid input reports a concise line, column, and UTF-16 character offset.
Preserving Large Numbers
Large integers, decimal zeros, negative zero, and exponent notation are preserved exactly.
Duplicate Object Keys
Duplicate keys remain valid and preserved, with a warning about how other software may interpret them.
UTF-8 Files and BOM Handling
The file picker accepts strict UTF-8 JSON and safely handles one leading BOM.
Private Local Processing
Parsing and output generation happen in a local browser Worker.
Copying and Downloading Output
Verified formatted or minified JSON can be copied or downloaded locally.
Frequently Asked Questions
Is my JSON uploaded?
No. Processing happens locally in your browser.
What makes JSON invalid?
Comments, trailing commas, bad escapes, invalid numbers, and extra root values are examples of invalid strict JSON.
Can I format a JSON file?
Yes. Open a UTF-8 .json file, edit it if needed, then choose Format.
Does formatting change numbers or notation?
No. The formatter preserves valid number lexemes exactly.
What happens to duplicate keys?
They are preserved and reported as a warning because some software keeps only the last value.
Can I minify JSON?
Yes. Minify removes only insignificant JSON whitespace.
Does it support comments or JSON5?
No. The tool accepts strict JSON only.
What is the maximum input size?
The maximum is 5 MiB of UTF-8 JSON text.
Does validation use JSON Schema?
No. Validation checks JSON syntax only.
Can I copy or download the result?
Yes, after successful formatting or minification.