Online JSON Generator: customize rows and fields to instantly generate sample JSON array data. Ideal for API testing, mock data, and frontend development. All processing is done locally.
TL;DR: Free online JSON generator. Produce sample JSON arrays in one click with custom row and field counts and diversified value types. Ideal for API testing, mock data, and frontend development. Local processing.
For local tools, open DevTools → Network and search your input — it should not appear in requests.
Next steps
Usage Guide
Integration testing, front-end mocks, documentation samples — hand-writing large JSON is slow and error-prone: missed fields, wrong types, broken nesting. The value is not realistic data but a correct shape — field names, types, and hierarchy matching the real API — because that is what your comparisons actually run against. Generated locally, nothing uploaded.
1. How to use
Start from a correctly-shaped skeleton and fill values in — an order of magnitude faster than typing from a blank file, and nested fields never go missing.
- Pick the shape (object/array, field count, nesting depth) and field types as needed.
- Preview the generated JSON; copy or download.
2. Why shape beats values
Mock data’s destination is code: front ends render by field, tests assert by type, docs align by structure. A misspelled field, a number quoted as a string, a missing optional — these shape errors propagate straight into integration. Values, by contrast, can be anything (example.com addresses, test phone ranges); the shape must match the API contract exactly. The working method: verify structure against the API doc first, readability second.
3. Type honesty: the three classic traps
- null is not "": one means “absent”, the other “empty text” — serializers treat them entirely differently.
- Numbers without quotes: id/count/price as strings skew both TypeScript inference and assertions.
- Booleans are booleans: "true" instead of true is the classic toggle-field mistake.
- Want types? Feed the sample to the in-site json-to-typescript for a type skeleton, then tighten optionality by hand.
4.
Mocking list pages with only the “many items” case is the most common oversight. Empty arrays drive the empty-state UI (placeholders, guidance copy); a single item drives the non-paginated layout; many items drive scrolling and pagination.
5. Division of labor with the random-data generator
This page owns the structural template: controlled shape, predictable fields — ideal for integration and docs. When you need bulk realistic random data (names, emails, addresses, timestamps) for demos or load tests, use the in-site mock-data generator. The common pipeline: define the shape here, let the random tool fill the flesh.
6. The sensitive-data red line
Never paste real user data in as samples — recordings, shares, and screen casts create second-hand leaks. Use obviously fake data (example.com addresses, test number ranges, synthetic IDs from the in-site generator). Real data in mocks is a top source of privacy incidents; this tool chain is fully local, but what you type in remains your responsibility.
7. Downstream chain
- Formatting and sorting: the in-site JSON Formatter normalizes indentation and key order.
- Structure as assertion: pair with json-schema-validator to freeze the shape contract in executable form.
- For non-engineers: json-to-excel turns the sample into a shareable table.
FAQ
The generation shape — object or array, number of fields, nesting depth — plus common field types as needed. Preview it, copy or download in one click, paste into a mock service, test fixture, or doc example, then swap in business values for the key fields.
Because mocks end up in code: a misspelled field name, a number quoted as a string, or a missing optional field pollutes integration all the way down. Values can be loose, but always obviously fake (example.com emails, test number ranges) — real user data in mocks is a classic source of privacy incidents.
Three frequent ones: null and the empty string mean different things and serialize differently on the backend; id, count, and price should not be quoted as strings; booleans are true/false, not the 'true' string. For a type draft, feed the result to the in-site json-to-typescript tool.
At least three: an empty array drives the empty-state UI (placeholders, guidance copy), a single item drives the non-paginated layout, and many items drive scrolling and pagination. Save one fixture per state and switch between them so edge behavior is not missed.
This page is the structural template: controllable shape and predictable fields, ideal for integration and doc samples. When you need large volumes of realistic random data (names, emails, addresses, timestamps), use the in-site mock-data-generator — define the shape here, then let the random tool fill it in.
No — open the page and use it. Sample JSON is generated locally, with no account and no paywall.
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