How json prettify vs minify works
The tool parses your JSON once and re-serializes it two ways: pretty-printed with your chosen indentation, and minified to a single line with all whitespace removed. Both are displayed at once so you can compare the human-readable and wire-optimized forms of the same document.
Minification removes the spaces, newlines and indentation that make JSON readable but add bytes. For API payloads this can measurably reduce transfer size. The tool reports the exact character savings and the percentage reduction so you can judge whether minification is worth it for your document.
If the input is not valid JSON, the tool reports the parser error without producing partial output, so you never copy a broken result. The indent is configurable for the pretty form.