JSON Schema Faker vs Snowfakery

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.

Snowfakery generates synthetic data from YAML recipe files, including records linked across tables. Recipes can create names, addresses, text, URLs, random numbers and other values using Faker-based functions, and specify how many related objects to generate. Output can go to files in JSON, TXT, CSV, SQL, DOT, SVG, SVGZ, JPEG and PostScript formats; some diagram formats require Graphviz. Snowfakery can also write to databases accessible through SQLAlchemy, including SQLite, and generate records in Salesforce when used through CumulusCI. Python applications can embed it with its generate_data function, and Python plugins and providers can extend its functions and Faker capabilities. Strict mode checks a recipe before generation, while validate-only mode checks it without generating data. It is free, open source and self-hosted. The documentation says database output creates new tables, with generated columns as text, and that SQLite is the only database included in its SQL dataset URL test suite. The repository was archived on September 18, 2026, and is read-only.