Chance.js vs JSON Schema Faker

Chance.js is a free, MIT-licensed JavaScript library for generating pseudorandom data used in automated tests and other applications needing sample values. Generators cover basic values, text, people, mobile identifiers, web data, locations, dates, finance, helpers, and miscellaneous categories. Developers can install it with npm for Node.js, load it in a browser, or use the separate chance-cli package from the command line. Browser users may create a global instance or instantiate several instances. Supplying a seed makes output repeatable; instances given the same seed can produce the same sequence. Integer generation accepts inclusive minimum and maximum bounds, and the unique() helper builds arrays without repeated generated items. The documented name generator supports English and Italian nationality options. The site lists chance.js at 95KB uncompressed and chance.min.js at 55KB, or 17KB gzipped. Chance is not intended for cryptographic applications requiring true randomness. The site credits Victor Quinn as its writer.

JSON Schema Faker generates synthetic JSON data from JSON Schema definitions. It supports JSON Schema 2019-09 and 2020-12, and a numeric seed can make results repeatable. The `jsf` command can read schema files, save generated JSON to a file, and produce multiple items as an array. Reference support includes `$ref` resolution with cycle detection, adjustable recursion depth, and remote reference resolution. Built-in generators cover formats such as email, date-time, URI, IP addresses, and UUID; regex patterns are supported through an AST-based string generator. Users can register custom formats and keyword generators, with optional extensions for faker.js and chance.js. YAML output requires the YAML package through an extension. The project runs in Node.js and browsers and is built for Bun and Node.js. It is self-hosted and open source under the MIT License, with zero production dependencies. The listed plan costs nothing. One constraint: synchronous generation works only when schemas resolve without I/O; asynchronous resolvers or extensions cause it to throw.