Minify

Minify is the process of removing every optional character from a document — whitespace, comments, unnecessary punctuation — to produce the smallest equivalent form. For JSON, minification removes all whitespace between tokens. For JavaScript, CSS, and HTML, it also shortens variable names and rewrites structures where possible.

A before-and-after

Pretty:

{
  "user": {
    "id": 42,
    "roles": ["admin", "editor"]
  },
  "active": true
}

Minified:

{"user":{"id":42,"roles":["admin","editor"]},"active":true}

Same data, ~30% smaller on the wire.

Why minify

• Bandwidth. At scale, a 30% raw-byte reduction across millions of requests is real money.
• Parse speed. Less text means less tokeniser work.
• Cache density. Smaller documents mean more fit into any given cache.
• One-packet payloads. A response that fits into a single TCP segment ships in one round trip. Minifying can slip a payload under that threshold.

The compression question

Minifying is largely redundant with HTTP compression. gzip or brotli on pretty-printed JSON gets close to the same wire size as gzipped minified JSON. The remaining savings are 3-10% after compression. Not nothing, especially at scale, but not dramatic.

The counter-argument is that minifying has other benefits — smaller browser cache entries, smaller IndexedDB blobs, smaller URL parameters — that compression does not help with.

Where minifying matters more

• Inside URLs (data URIs, query parameters) — no compression available.
• Offline storage that does not re-compress (e.g. IndexedDB, localStorage).
• High-frequency small messages where the compression overhead outweighs the savings.
• Tight memory budgets on constrained devices.

Where minifying matters less

• Any endpoint served behind a CDN with gzip/brotli enabled.
• Payloads large enough that compression does most of the work.
• Response formats read by developers during debugging (where pretty is worth keeping).

Tooling

• JSON: JSON.stringify(obj) (no indent argument = minified). jq -c . on the command line.
• JavaScript / TypeScript: esbuild, terser, swc — all ship heavy minifiers including variable-name shortening.
• CSS: lightningcss, cssnano, esbuild.
• HTML: html-minifier-terser, rehype-minify-whitespace.

For when and when not to minify wire payloads, see When minifying API payloads actually matters.