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JSON duplicate keys, Unicode, and escaped-character test

Does the JSON formatter reject malformed syntax while preserving ordinary Unicode—and what happens to duplicate keys and unsafe integers?

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Recorded output for JSON duplicate keys, Unicode, and escaped-character test
Recorded first-party output associated with this report.

Test environment

Chrome 154.0.8037.97 and Edge 154.0.4258.53; 1100 × 850 viewport.

Fixture and expected result

Malformed JSON is rejected and stale output is cleared. Unicode strings remain readable. The duplicate-key and unsafe-integer controls expose parser limitations rather than being treated as safe transformations.

Reproduction steps

  1. Download the JSON fixture.
  2. Paste it into the formatter and choose Minify JSON.
  3. Compare the displayed output with the published recorded result.
  4. Repeat with the numeric identifier as both a number and a string.

Observed result

All 14 recorded cases matched the fixed expectations in both browser runs. The repeated role key produced only the final value, and 9007199254740993 serialized as 9007199254740992; the string form remained exact.

Downloadable evidence

The fixture library publishes SHA-256 hashes for exact-byte verification.

What this test does not establish

This is not a complete JSON conformance suite. Successful parsing does not validate an API schema, detect every duplicate before parsing, or preserve arbitrary-precision numbers.

Related tool and guide

JSON Formatter & Validator · Why Valid JSON Still Breaks APIs

Change history

  • : Structured data, image dimensions, and fixture links reviewed.
  • : Report organized under Anvil Tools Lab; evidence and limitations reviewed.