JSON Forge
100% Client-Side: your data is never sent to a server

JSON Diff

Find out exactly what changed between two JSON documents. Both sides are normalized first, so formatting differences and (optionally) key order do not show up as noise.

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Paste or type JSON on the left to explore it as a tree.
Empty🔒 Processed locally in your browser

How to compare two JSON files

  1. Put the first JSON in the editor on the left.
  2. Paste the second JSON into the comparison box in the Diff tab.
  3. Review added (green) and removed (red) lines. Turn on Changes only to hide everything else.

How the comparison works

Both documents are parsed, normalized to the same indentation and, by default, sorted by key. A line-by-line diff then highlights what was added and removed. This avoids the false positives you get when comparing raw text where only the formatting differs.

Common uses

Compare API responses before and after a deploy, check a config change, verify a data migration, or find out why two environments behave differently. Turn on Changes only to collapse everything that is identical.

What is JSON?

JSON (JavaScript Object Notation) is a lightweight, text-based data format that is easy for people to read and for machines to parse. It is the de facto standard for web APIs, configuration files and data exchange between services. A JSON document is built from just six value types: objects, arrays, strings, numbers, booleans and null.

{
  "name": "Ada",
  "age": 36,
  "admin": true,
  "skills": ["math", "code"],
  "address": { "city": "London" },
  "manager": null
}

JSON is stricter than JavaScript object literals: keys and strings must use double quotes, trailing commas are not allowed and comments are not part of the specification (RFC 8259).

Why format JSON?

APIs usually return minified JSON on a single line, which is efficient for machines but unreadable for people. Formatting (also called pretty printing or beautifying) adds consistent indentation and line breaks so that you can scan the structure, spot mistakes and review changes. Minifying does the opposite and strips whitespace to reduce size.

Frequently asked questions

Does key order matter?

By default it is ignored: keys are sorted before comparing, so only real data changes are highlighted. Untick Ignore key order to compare documents exactly as they are.

Is my JSON uploaded to a server?

No. Parsing, validation, formatting, diffing and code generation all run inside your browser, using a Web Worker. Your data is never sent to any server, which makes the tool safe for API responses, configuration files and other sensitive payloads.

Does it work offline?

Yes, after the first visit. The editor and tools are stored in your browser, so you can use them without a connection. Only the TypeScript, CSS and HTML language workers used for extra highlighting in the Code tab are downloaded the first time you use them.

How large a JSON file can I open?

Files of 20 MB and more work. Parsing happens off the main thread and the tree view is virtualized, so only the rows you can see are rendered. The editor switches to a lighter mode for very large documents.

What is the difference between formatting and minifying JSON?

Formatting (pretty printing) adds line breaks and indentation so people can read the data. Minifying removes all optional whitespace to make the payload as small as possible for network transfer or storage. Both produce identical data.

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