API Mock Data Generator
Generate reproducible API test data from a JSON sample by configuring field rules, output shape, item count, locale, and seed in your browser.
Mock data generation
Paste JSON or load a preset or JSON file.
Input JSON
Direct inputGenerated result
Read-onlyField generation rules
You can check the automatically determined rules and change only the necessary items.
Setting value format: Sequential number "start value, increment" / candidate "value 1, value 2" / numerical value "minimum value, maximum value" / date "start, end"
| JSON path | Type | Generation rule | Setting value | sample value |
|---|
Generated result
Using the same seed and settings reproduces the same mock data.
- generated record
- 0
- Fields
- 0
- generated value
- 0
- Number of output characters
- 0
About this tool
Create JSON mock data from sample structures for API screen development, pre-integration testing, demo, and test data preparation.
Features
- Estimation of JSON structure including object/array
- UUID, name, email, phone, address, URL, IP, sequential number, candidate value, numerical value, date
- Single/Array/Pagination format
- Reproduction by seed, copy, save UTF-8 JSON
How to use
- Enter the JSON sample and press "Parse Structure".
- Adjust the generation rules and number of items for each field.
- Press “Generate Mock” and check the result.
- Copy the results or save them as a JSON file.
Limitations
- This tool generates JSON data; it does not run a mock server or expose an API endpoint.
- It does not support complete loading of OpenAPI/JSON Schema or complex dependencies between items.
- Generating a large amount of data uses the device's memory, so first check with a small number of data.
Privacy: The input JSON and generated results are processed only within the browser and are not sent or saved to the Develop Tools server.