Chance.js vs Faker.js

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.

Faker.js is a free JavaScript library for generating synthetic data that resembles realistic information during testing and development. Its modules produce person, location, date, finance, commerce, and other data. Documented uses include unit tests, performance tests, demos, and development before a backend is complete. Pre-built instances cover more than 70 locales, and custom locales can be created. The implementation runs in browsers and Node.js; Faker v10 requires Node.js 20 or newer. Installation guidance covers npm, pnpm, yarn, and Deno, with examples for Vitest, Jest, Cypress, and Playwright. A seed can make generated values repeatable, although identical seeds may produce different results between Faker versions. The full package exceeds 5 MiB when minified, and its guide advises against deploying the entire package in a web app. Locale coverage varies, with some combinations using English fallback data or lacking applicable data. Faker is MIT licensed for commercial and non-commercial use and is self-hosted.