Sample JSON Generator

What each field type produces

There are 19 value types plus Object and Array:

• Text: Word, Sentence and Paragraph give Latin-style placeholder text of growing length.
• Numbers: Number gives a whole number from 0 to 1000, Small number from 1 to 10, and Price a value from 1 to 1000 with up to two decimals, such as 664.25. Index is the position of the record or array item, starting at 1.
• Boolean gives true or false. Null always gives null.
• UUID gives a version 4 UUID from the browser's crypto.randomUUID(). Date (ISO) gives a UTC timestamp like 2023-08-06T12:39:59.110Z from the last 5 years.
• People and places: Full name, First name, Email (lowercase), Phone (US format, like (213) 378-3310), Address (street, city, state and ZIP on one line, like 427 Eryn Center, Port Juan, NM 14700), Company, URL and Product name.

Cover the edge cases, not only the happy path

Real API data is messier than a demo. A few settings make the mock closer to what your code will meet in production:

• Set an array's Length to 0 to check the empty state of a list, a table or a search page.
• Add a Null field where the real API sometimes leaves a value out, such as deletedAt or avatar.
• Use Paragraph in a field that's normally short, like a title, to see how your layout handles long text.
• Generate 1,000 records to test sorting, filtering and scrolling with a realistic amount of data.
• Keep IDs unique with Index or UUID. Number can repeat across records.

Serve the JSON as a mock REST API

JSON Server turns a JSON file into a REST API for local development. It needs an object at the top level, so generate an array of records here and put it under a key, such as users. Save the file as db.json and run the command below. You get GET /users, GET /users/:id, POST /users, PUT and PATCH /users/:id, and DELETE /users/:id at http://localhost:3000.

{
  "users": [
    { "id": 1, "name": "Jaydon Tremblay", "email": "alessia_gottlieb59@gmail.com" },
    { "id": 2, "name": "Chaz Sauer", "email": "unique.stamm@gmail.com" }
  ]
}

npx json-server db.json

Generate sample data in code

For test suites and seed scripts, create the data in code with a fixed seed. The same seed gives the same values on every run, so a failing test fails the same way twice.

import { faker } from "@faker-js/faker";

faker.seed(123);
const users = faker.helpers.multiple(
  () => ({
    id: faker.string.uuid(),
    name: faker.person.fullName(),
    email: faker.internet.email(),
  }),
  { count: 5 }
);

from faker import Faker

Faker.seed(123)
fake = Faker()
users = [
    {"id": fake.uuid4(), "name": fake.name(), "email": fake.email()}
    for _ in range(5)
]