# Negative Payload Generator | Generate invalid request bodies from schemas

Missing rejection tests? Generate invalid payloads for supported schema rules and inspect each failing constraint. Check locally in your browser. No upload.

Canonical: https://tamperbox.dev/negative-payload-generator

Docs: https://docs.tamperbox.dev/tools/negative-payload-generator.md

Updated: 2026-10-26

Reviewed: 2026-10-26

## How it works

Negative Payload Generator reads json schema or openapi json locally and presents findings with the evidence behind them. A synthetic order schema requires a short name and a quantity between one and five. The full method, every rule and worked examples are on [docs.tamperbox.dev](https://docs.tamperbox.dev/tools/negative-payload-generator/).

## Limits and interpretation

A bounded subset of JSON Schema is supported; unknown validation keywords are refused. Generated failures do not test authorization or application business rules. Inputs are limited to 1,000,000 characters per field. Nothing is fetched from addresses embedded in input. Explicit copies and downloads are under your control.

## Frequently asked questions

### Is my input uploaded?

No. Parsing and output generation run in your browser. Source values are not sent to a server.

### What does the opening example demonstrate?

A synthetic order schema requires a short name and a quantity between one and five. It is synthetic data. Replace it with your own input to inspect a different case.

### Does a passing result prove my application works?

No. A bounded subset of JSON Schema is supported; unknown validation keywords are refused. Generated failures do not test authorization or application business rules. Verify the result in your test environment before relying on it.

## References

- [Primary format and behavior reference](https://json-schema.org/draft/2020-12/json-schema-validation).