How to minify JSON

Minifying JSON removes all the whitespace that exists only for human readers: spaces, tabs and line breaks between tokens. The data itself is unchanged, and any JSON parser reads the minified version exactly as it reads the formatted one. This guide covers how minification works, how much it really saves, and when it's worth doing.

Before and after

Pretty printed:

json
{
  "a": 1,
  "b": [
    1,
    2,
    3
  ],
  "c": "hello"
}

Minified:

json
{"a":1,"b":[1,2,3],"c":"hello"}

Whitespace inside strings is part of the data, so a minifier leaves "hello world" alone. Only whitespace between tokens is removed.

How to minify JSON

In the browser: paste your JSON into the JSON Formatter and click Compact. The editor validates the input first, so you'll know immediately if something is wrong.

In JavaScript: JSON.stringify without an indent argument produces minified output:

javascript
const minified = JSON.stringify(JSON.parse(text));

In Python: pass compact separators, otherwise Python adds a space after : and ,:

python
import json
minified = json.dumps(data, separators=(",", ":"))

On the command line: jq -c . input.json prints compact output.

How much does it save?

For typical pretty-printed API responses, minification removes roughly 10–30% of the bytes, depending on nesting depth and indent size. Deeply nested data with four-space indentation shrinks the most.

That sounds significant, but on the web most JSON is also compressed with gzip or Brotli before it's sent. Compression is very good at squeezing repeated whitespace, so after compression the difference between minified and pretty-printed JSON is often only a few percent. Minifying is still worthwhile at scale, but compression matters far more. Check that your server sends Content-Encoding: gzip or br before optimizing anything else.

When minifying helps

• High-volume APIs, where a few percent per response adds up across millions of requests.
• Storing JSON blobs in databases, caches or local storage, where size limits apply and data isn't compressed.
• Embedding JSON in HTML, URLs or environment variables, where line breaks cause problems. Note that sharing JSON through a URL has length limits; see How to share JSON data.
• Log lines, where each event should be a single line. That's the idea behind NDJSON / JSON Lines.

When not to minify

• Files people edit or review, such as configuration files and test fixtures. Minified JSON makes code review and diffs almost impossible to read.
• While debugging. Pretty print first, find the problem, then minify if you need to. See How to pretty print JSON.
• Before comparing documents. Compare formatted versions so differences show up line by line.

Minification is not obfuscation or security

Minified JSON is just as readable to anyone who runs it through a formatter. Don't rely on it to hide data. If a payload contains secrets or personal information, remove or mask them first; see Redact / sanitize JSON.

Common problems

If minification fails, the input isn't valid JSON. The usual causes are trailing commas, comments and single quotes; see Validate JSON. If the output looks "too small", check whether a tool also dropped null values or empty objects. A true minifier never removes data.