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Download a Sample JSON File (Any Size)

Generate and download a sample JSON file at any exact size — free, in-browser, no signup.

JSON is the default payload format of the modern web, and a tiny hand-written fixture will never reveal how your application behaves under realistic API response sizes. The generated file is a valid JSON array of objects — passes JSON.parse() without error — scaled to whatever exact byte count you need. It is made entirely in your browser, so no payload leaves your machine before you are ready to use it.

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1 MB (1,000,000 bytes)

Generated entirely in your browser — nothing is uploaded.

Common JSON test sizes

Each preset is generated in your browser at exactly that many bytes (decimal: 1 MB = 1,000,000 bytes). For any other size, use the generator above.

100 KB sample JSON file

One hundred kilobytes of JSON is the kind of payload a list API returns when pagination is set too high — several hundred objects that a frontend should be processing in batches but often is not. Use it to test JSON rendering performance in your data table components and to confirm your API client handles a response larger than a trivial fixture. Valid, passes JSON.parse(), generated in your browser.

1 MB sample JSON file

A 1 MB JSON payload is where JavaScript's main-thread JSON.parse() starts to cause noticeable UI jank, and where API gateways with default 1 MB body-size limits will start rejecting requests. Use it to benchmark your parser, test your gateway configuration, and confirm your frontend handles large list responses without freezing the tab. Valid JSON, generated entirely in your browser.

10 MB sample JSON file

Ten megabytes of JSON crosses the threshold of most API gateway body limits and is large enough to measure the real cost of non-streaming JSON parsing. Use it to compare streaming JSON parsers (like oboe or JSONStream) against JSON.parse(), to benchmark your data serialization layer, or to test whether your system correctly returns a 413 Payload Too Large error before a client sends this volume. Generated in your browser.

Common use cases for JSON test files

  • Stress-testing JSON parsers, API clients, and frontend data rendering components
  • Verifying API gateway body-size limits and response streaming behavior
  • Generating realistic mock data volumes for frontend development and load testing
  • Benchmarking JSON serialization and deserialization performance at scale

Related formats

Sample File Generator — all 20 formats, any exact size, free in-browser download.

Frequently asked questions

Is the generated JSON actually valid?

Yes. It is a top-level array of objects with consistent keys (id, name, value, tags, createdAt). JSON.parse() and any JSON schema validator will accept it without errors or warnings.

Why would I need a 10 MB JSON file for testing?

To surface real-world problems — browser tab memory limits, streaming parser timeouts, frontend rendering lag with large data sets, and API gateway body size caps. A 10 KB fixture does not expose any of those failure modes.

Can I use this as mock API data for a frontend app?

Yes. The structure mimics a typical REST list endpoint response, which makes it useful for testing pagination, virtual scrolling, and data table rendering with a volume you might actually see in production.

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