JSON minifier

When to minify JSON

Pretty-printed JSON is easy to read but carries a lot of whitespace: indentation and line breaks can be a third of a file. Minified JSON drops everything outside strings that does not change the data. It is what you want in environment variables, query parameters, HTTP request bodies, and anywhere a value must fit on one line.

For data sent over HTTP with gzip or Brotli compression, the size difference after compression is small, so minifying matters most for storage limits and single-line fields.

Worked example

{
  "id": 42,
  "tags": ["a", "b"],
  "note": "keep  these  spaces"
}

minifies to {"id":42,"tags":["a","b"],"note":"keep these spaces"}, from 69 to 55 bytes. The double spaces inside the string are data, so they stay.

The input is parsed with the strict JSON parser used by the other JSON tools, so invalid input is reported with its line and column rather than minified into something broken. The parsed value is then written back without any optional whitespace. Numbers come out in JavaScript's shortest form (1.50 becomes 1.5), escapes are normalised, and key order is kept. The byte counts are UTF-8 lengths of the input and the output. Everything runs in this tab.