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JSON Minifier

Last updated: 26 September 2026

Compress any JSON to its shortest legal form by stripping indentation and line breaks — and see exactly how many bytes that saved. It runs in your browser, so the payload never leaves the machine.

What minifying JSON does

A pretty-printed document spends a surprising amount of its length on characters the parser ignores: two-space indents, one property per line, the space after every : and ,. Minifying removes all of it and collapses the file onto a single line. The result is byte-for-byte equivalent as data — JSON.parse returns the identical value before and after — because whitespace between tokens is not part of the information.

The one thing minification never touches is whitespace inside a string. A value such as " keep me " survives intact, since there it is data rather than formatting.

When you want minified JSON

• HTTP request and response bodies — every kilobyte is paid for on each call, and mobile round trips are the ones users feel.
• Embedding JSON in a page or bundle — an application/json script block, a fixture inlined in a test, a config object shipped to a client.
• localStorage and sessionStorage — the quota is a fixed per-origin budget (about 5 MB in most browsers), and exceeding it throws a QuotaExceededError rather than degrading quietly.
• Query parameters and form fields — percent-encoding inflates whitespace roughly threefold, so the savings are bigger than they look.
• Storing documents in a database column or cache entry where the size is billed or bounded.

Conversely, leave config files that humans edit and review formatted. The byte saving is irrelevant on disk, and single-line JSON in a diff is unreadable.

How much smaller does it get?

Roughly what the formatting costs you. A document indented two spaces per level with one key per line commonly loses 20–45% of its length; deeply nested payloads with wide indents lose more. Payloads dominated by long strings barely move, because there is almost no formatting in them to remove. The tool reports the real number for your own data rather than an estimate.

Minify from the command line or code

A browser tab is the right tool for pasting one-off payloads. For pipelines, do it where the file already is:

• jq -c . config.json > config.min.json — compact output, one line per top-level value.
• python3 -c "import json,sys;sys.stdout.write(json.dumps(json.load(sys.stdin),separators=(',',':')))" < config.json — the tightest form, no space after separators.
• node -e "process.stdout.write(JSON.stringify(JSON.parse(require('fs').readFileSync(process.argv[1],'utf8'))))" config.json — the same semantics as this page.

In application code the last two matter more than the file: build the payload with JSON.stringify(value) and it is already minified — the null second argument is what keeps it compact, since JSON.stringify(value, null, 2) is what adds the indentation back.

Minification and compression are different jobs

They stack rather than compete. Minification removes formatting first; gzip or Brotli then compresses what is left, and for anything sent over the wire the transfer encoding is the bigger win — a minified-then-gzipped payload often ends up far smaller than either step alone. Minify anyway when the bytes are stored rather than streamed, because nothing is compressing them for you.

Frequently Asked Questions