JSON test-file generator

Generate a synthetic JSON file of any size — up to 50 GB — right in your browser and stream it straight to disk. Use the file to benchmark the JSON viewer, your own parser, or any JSON tooling. Nothing is uploaded — the bytes go from your browser to a file you pick.

Target size

Output format

A top-level JSON object. The first key is always a header so you can identify the file and when it was generated:

{
  "generated": { "by": "omniviewer.org", "on": "<ISO-8601 timestamp>" },
  "<word>_0": <value>,
  "<word>_1": <value>,
  ...
}

Values are a mix of strings (English & French words, multi-byte UTF-8), numbers (integers and floats), booleans, null, and nested objects/arrays up to depth 8. This shape compresses similarly to real-world JSON, so parse-throughput measurements are representative.

How it works

Where the browser supports the File System Access API (showSaveFilePicker — Chrome, Edge, Opera), the JSON streams to your chosen file ~1 MB at a time in a background worker; generating the next chunk overlaps with writing the previous one, and there is no in-memory buffer of the whole file — so a 50 GB file costs the same memory as a 50 KB one. On Firefox and Safari it falls back to assembling a Blob in memory and downloading it — fine for modest sizes, but large files may run into the browser's memory limits.

What to do with the file

Drop it onto the JSON viewer to test parse throughput on your hardware.
Feed it to simdjson, jq, node, etc. and compare parse times.
Use it as input to load-testing scripts that need realistic JSON payloads at scale.