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JSON Minifier

In-browser only RFC 8259 JSON parser
Result
The result appears here once you enter JSON.
Runs entirely in your browser with the built-in JSON parser.
Related tools View all

Overview

Format, validate, minify, and lint JSON in your browser

Strip every byte of unnecessary whitespace from JSON. See the original size, the minified size, and exactly how much you saved.

  • Format, validate, minify, and lint from one panel
  • Exact line and column for every syntax error
  • 2-space, 4-space, or tab indentation
  • Catches duplicate keys, trailing commas, and comments
  • Runs entirely in your browser
  • All processing runs entirely in your browser
  • Your JSON data is never uploaded to any server
  • Nothing is stored — the page holds no state between sessions
  • No account or login required to use any feature
  • Inspect the network tab to confirm zero outbound requests
  • Shrink JSON for transport or storage
  • Cut bytes before gzip or brotli
  • Compact a payload for a size-limited field
  • Reduce cache and storage footprint
  • Strip whitespace from a config bundle

Guide

How to use

  1. 1
    Paste your JSON

    Type, paste, or use the Paste button to pull JSON from your clipboard. The Sample button loads a small example to try.

  2. 2
    Choose an action

    Switch between Format, Validate, Minify, and Lint using the tabs. The same input is reused — no need to paste again.

  3. 3
    Read the result

    Formatted and minified output appears in the result pane; validation shows a clear verdict; lint lists every issue with its location.

  4. 4
    Copy or download

    Use Copy to send the result to your clipboard. On the Format and Minify tabs you can also Download the result as a .json file.

Reference

What JSON Lint checks

JSON lint issues and what they mean
IssueWhat it means
Duplicate keyTwo properties in one object share a key — parsers keep only one value.
Trailing commaA comma before a closing bracket or brace — not allowed in strict JSON.
Comment// or /* */ comments — valid in JSON5/JSONC but rejected by JSON.
Single-quoted stringStrings or keys in single quotes — JSON requires double quotes.
Unquoted keyAn object key without quotes — JSON requires every key to be double-quoted.
Byte-order markA hidden BOM character at the start of the input that can confuse parsers.

Pitfalls

Common JSON mistakes

  • Trailing commas

    A comma after the last item in an array or object is fine in JavaScript but invalid in JSON. Remove the comma before the closing bracket or brace.

  • Single quotes

    JSON requires double quotes for every string and key. Single quotes are a JavaScript habit — the Lint tab flags each one so you can swap them.

  • Unquoted keys

    JavaScript object literals allow bare keys like {name: "x"}, but JSON needs {"name": "x"}. Every key must be wrapped in double quotes.

  • Comments

    JSON has no comment syntax. // and /* */ comments are valid in JSON5 and JSONC but a standard parser will reject them — strip them before parsing.

Frequently asked questions

How much smaller does JSON get when minified?
It depends on how much whitespace the input has. Pretty-printed JSON with 2-space indentation typically shrinks 20–60%. JSON that is already compact may shrink very little.
Is minified JSON still valid?
Yes. Minification only removes insignificant whitespace between tokens. The data and structure are identical, and any JSON parser will read the result the same way.
Should I also compress my JSON?
For network transfer, yes — gzip or brotli compression on top of minification typically achieves much larger total savings. Minifying first removes redundant whitespace before compression runs.
Does minifying change key order?
No. Minification preserves the order of keys exactly as they appear in your input.