Paste a JSON document and the minifier parses it, then writes it back out with no whitespace between tokens. Spaces inside strings are kept. For example, { "a": 1, "b": [1, 2] } becomes {"a":1,"b":[1,2]}, shrinking from 23 to 17 bytes, a 26.1% reduction. Invalid JSON is reported instead of being guessed at.
Pretty-printed JSON is easy to read in a diff but wasteful in a request body, an environment variable or a config value pasted into a single-line field. This minifier parses your input with the same strict grammar browsers use, so a trailing comma or a single-quoted key is caught rather than passed along. It then re-serialises the data compactly and reports the UTF-8 size before and after, plus the bytes removed. Because the output is rebuilt from parsed values, a few representations can change: 1.50 becomes 1.5, and integers beyond 2^53 lose precision. Everything runs locally in the page; the document is never uploaded.
Paste it into the box or open a .json or .txt file from your device.
If parsing fails, the message under the box names the problem, such as an unexpected token.
Copy the single-line output and check the byte sizes and percentage removed.
Result Minified JSON: {"a":1,"b":[1,2]}
Original size (bytes): 23
Minified size (bytes): 17
Bytes removed: 6
Size reduction: 26.1%
Six spaces after colons and commas go, taking 23 bytes down to 17, a 26.1% cut.
Result Minified JSON: {"name":"Ada","tags":["math","engines"]}
Original size (bytes): 62
Minified size (bytes): 40
Bytes removed: 22
Size reduction: 35.5%
Line breaks and indentation are removed, leaving 40 bytes on a single line.
Result Minified JSON: ["hello world",3]
Original size (bytes): 21
Minified size (bytes): 17
Bytes removed: 4
Size reduction: 19%
Only whitespace between tokens is dropped; the space in "hello world" is part of the value and stays.
minified = JSON.stringify(JSON.parse(input)); reduction = (original bytes − minified bytes) ÷ original bytes × 100
original bytesminified bytesRFC 8259 treats spaces, tabs, carriage returns and line feeds between tokens as insignificant. Parsing the text and serialising it with no indent removes all of them while leaving string contents untouched. Sizes are counted in UTF-8 bytes, the encoding JSON must use on the wire, so an accented letter counts as two bytes and an emoji as four.
The values stay the same, but some spellings can change: 1.50 is written as 1.5, 1e3 as 1000, and an escaped \u00e9 as é. Key order is preserved. Integers above 2^53 lose precision, because parsing stores numbers as double-precision floats.
No. Only whitespace between tokens is removed. A string such as "hello world" keeps its space, and line breaks inside strings remain as \n escapes.
Compact JSON that already uses short indentation has little whitespace to lose, often 10 to 30 percent. Deeply nested documents with four-space indentation shrink more, sometimes by half.
Gzip and Brotli compress repeated whitespace very well, so the transfer saving after compression is usually small. Minifying still helps where compression is absent, such as storage limits, query strings or single-line config values.
The parser follows RFC 8259 strictly. Trailing commas, single quotes, comments, unquoted keys and values such as NaN or undefined are all invalid JSON and produce an error naming the problem.
No. Parsing and serialising happen in your browser, and a file you open is read locally without being uploaded.
Using this tool in an assignment, article or report? Copy a citation, or a link for your website.
Tools Directory Editorial Team. (2026, October 28). JSON Minifier. Tools Directory. Retrieved October 28, 2026, from https://tools.milunir.com/developer-tools/json-tools/json-minifier/
Tools Directory Editorial Team. “JSON Minifier.” Tools Directory, 28 Oct. 2026, https://tools.milunir.com/developer-tools/json-tools/json-minifier/. Accessed 28 Oct. 2026.
Tools Directory Editorial Team. “JSON Minifier.” Tools Directory. Last modified October 28, 2026. Accessed October 28, 2026. https://tools.milunir.com/developer-tools/json-tools/json-minifier/.
<a href="https://tools.milunir.com/developer-tools/json-tools/json-minifier/">JSON Minifier – Tools Directory</a>