Diff Shuttle

Compare JSON Online Free — Auto-Formatting JSON Diff Checker for API Responses and Config Files

JSON Diff Tool

Compare two JSON documents online and see exactly what changed. Diff Shuttle parses and reformats both sides with consistent indentation first, so minified versus pretty-printed noise disappears and only real changes to keys and values are highlighted. Perfect for API responses and config files. Free, instant, and fully private — everything runs in your browser.

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How to Compare JSON

  1. 1

    Add Your Two JSON Documents

    Paste the original JSON into the left box and the modified JSON into the right box. If your data lives in a file, use the Select File button or drag and drop a .json file onto either side. Files are read locally up to 10 MB each, and nothing is uploaded anywhere.

  2. 2

    Select JSON Diff Mode

    Choose JSON Diff from the mode menu. Both sides are parsed and reformatted with consistent two-space indentation before the comparison runs, so a minified payload and a pretty-printed one with the same data show no differences. Pick Side by Side or Unified view to suit how you like to read.

  3. 3

    Review and Export

    Read the highlighted output, where added lines are green, removed lines are red, and unchanged lines stay neutral, each with line numbers. Check the statistics panel for additions, deletions, and the difference percentage, then click Export as Text to download a report you can attach to a bug report or share with your team.

Why Use a JSON Diff Tool?

Formatting Noise Disappears

Because both sides are reformatted before diffing, a minified response and an indented one with the same content match perfectly. You see only genuine changes to keys and values, not differences in whitespace or line breaks.

Private by Design

Your JSON is never uploaded. Both inputs are parsed and compared entirely in your browser, which makes Diff Shuttle safe for API responses, tokens, and configuration data you cannot send to a third-party service.

Nested Changes Made Clear

Reformatting expands nested objects and arrays onto separate lines, so a change buried several levels deep shows up as a clearly highlighted line instead of being hidden in a long single-line blob.

Free With No Limits

There is no sign-up, no paywall, and no cap on comparisons. Side by Side and Unified views plus a text export of the result are all included at no cost.

Common Scenarios

Comparing Two API Responses

When an endpoint returns something unexpected, you often have a known-good response and the new one in hand. Paste both into JSON Diff mode and the changed fields light up instantly, even if one payload is minified and the other is pretty-printed. This turns a tedious manual scan of two long blobs into a few seconds of reading.

Reviewing Config File Changes

A misbehaving service is frequently caused by one altered value in a JSON config. Drop the previous and current versions into the tool, and the added, removed, or changed keys are obvious. Because everything stays local, you can safely diff configs that hold credentials or internal endpoints.

Validating a Data Migration

After transforming or migrating data, compare a record before and after to confirm only the intended fields changed. The difference percentage and the highlighted lines give you a fast, reliable sanity check before you trust the migration at scale.

Checking Package or Lock Files

JSON manifests such as package.json and similar files change often, and not every edit is intentional. A quick diff shows exactly which dependencies or settings moved, so you can confirm an update did what you expected before committing.

Tips and Best Practices

Make Sure Both Sides Are Valid JSON

JSON Diff mode shines when both inputs parse cleanly, because that is what lets it normalize formatting. If a side has a syntax error, the tool falls back to a plain text diff, so fix the error first for the clearest result.

Paste Minified JSON Without Worry

You do not need to pretty-print anything yourself. Drop minified JSON straight from an API call and the tool reformats it automatically, so a one-line payload becomes a readable, line-by-line comparison.

Use Side by Side for Big Objects

For large documents, Side by Side view keeps the two versions aligned so you can scan corresponding sections together. Switch to Unified for a compact, patch-style read when only a few keys changed.

Mind Key Order

Reformatting preserves the order of keys as written, so two objects with the same data but different key order may show differences. If that is noise for you, sort keys consistently in both inputs before comparing.

Export for the Record

Once the diff looks right, use Export as Text to save a report with plus and minus prefixes and a statistics summary. It is handy for attaching to a bug report or sharing the exact change with someone who does not have the tool open.

Compared to Alternatives

Many online JSON diff tools upload your data to a server to process it, which is a real concern when the payload contains tokens, user records, or internal configuration. Diff Shuttle parses and compares everything locally in your browser, so sensitive JSON never leaves your device, there is no account to create, and the auto-formatting and text export are free.

You can pretty-print two payloads by hand and run a generic text diff, but that is fiddly and easy to get wrong — one stray indent and the whole comparison turns to noise. Diff Shuttle does the normalization for you, reformatting both sides with consistent indentation before diffing so the result reflects content, not formatting.

Command-line tools like jq combined with diff are powerful for developers but require setup and comfort in the terminal. For a quick visual comparison of two responses you already have on the clipboard, a browser tool is faster and works for non-developers too, while still keeping your data private.

Frequently Asked Questions

Is the JSON diff tool free?

Yes. Diff Shuttle is completely free with no registration, no watermarks, and no limit on how many JSON comparisons you run.

Is my JSON uploaded to a server?

No. The comparison runs entirely in your browser. Both inputs are parsed and compared locally and nothing is sent anywhere, so API responses and config data with secrets stay private.

Does it format my JSON before comparing?

Yes. JSON Diff mode parses both sides and reformats them with consistent two-space indentation before diffing, so minified versus pretty-printed JSON will not show as differences — only real changes do.

What happens if my JSON is invalid?

If either side fails to parse, the tool gracefully falls back to a plain line-by-line text comparison so you still get a useful diff. Fix syntax errors so both sides are valid JSON for the cleanest result.

Can it compare nested objects and arrays?

Yes. After reformatting, nested structures are expanded onto separate lines, so changes deep inside objects or arrays appear as clearly highlighted added and removed lines.

Can I download the comparison?

Yes. Click Export as Text to download a plain-text report with added lines prefixed by a plus sign, removed lines by a minus sign, and a statistics summary of additions, deletions, and difference percentage.

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