genson
GenSON is a powerful, user-friendly JSON Schema generator.
Decision gist · record as of 2026-08-14
Yes. GenSON is actively maintained, has no external dependencies, supports current Python versions (3.10+), carries no known vulnerabilities, and solves a real problem—automating the tedious first step of schema creation. Use it when you need to generate or merge JSON schemas from data samples or existing schemas. The permissive MIT license poses no restriction.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Requires Python 3.10 or later.
- Low install friction with no runtime dependencies.
- Actively maintained as of 2026-07-06 with recent release history and stable production status.
License · maintenance · safety
MIT (permissive) — MIT license is permissive; you can use, modify, and distribute this package freely in commercial and private projects with minimal restrictions.
last release 2026-07-06 (39 days) · last repo commit 2026-07-06 · 725 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 19,370,440 downloads/mo, #1,068 on PyPI
Alternatives
Verify before relying
pip install genson
from genson import SchemaBuilder
builder = SchemaBuilder()
builder.add_object({"name": "Alice", "age": 30})
builder.add_object({"name": "Bob"})
schema = builder.to_schema()
print(schema)- Whether the package handles deeply nested or very large JSON structures efficiently.
- Performance characteristics when merging hundreds or thousands of schemas.
- Extent of customization available through extensibility for non-standard merging behavior.
What it is and what it does
GenSON is a JSON Schema generator that takes JSON objects as input and produces JSON Schema documents describing their structure. Its core strength is the ability to merge schemas: you can feed it multiple JSON objects or existing schemas, and it will generate a single unified schema that accommodates all of them. The package follows three guiding rules: every input object must validate under the generated schema, any object valid under any input schema must also validate under the output, and the schema should be as strict as possible given those constraints.
The package works with JSON Schema Draft 6 and above, though it uses only a subset of JSON Schema's keywords (type, properties, items, required, anyOf, enum, and a few others). It includes both a Python API via the SchemaBuilder class and a command-line tool for schema generation. GenSON is designed to help you skip boilerplate schema writing by inferring basic structure from your data, leaving detailed constraints for manual refinement.
Use it for
- Automatically generate baseline JSON Schema from sample API responses to jumpstart validation rules.
- Merge schemas from multiple data sources to find the common structure across heterogeneous datasets.
- Build schema validators for incoming JSON data by inferring constraints from known-good examples.
- Generate documentation schemas from production JSON objects without manual schema authoring.
- Combine hand-written schemas with inferred ones to progressively refine data validation rules.
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes.
GenSON is actively maintained, has no external dependencies, supports current Python versions (3.10+), carries no known vulnerabilities, and solves a real problem—automating the tedious first step of schema creation. Use it when you need to generate or merge JSON schemas from data samples or existing schemas. The permissive MIT license poses no restriction.
Install
genson on PyPI
Before you install
Low install friction with no runtime dependencies. Actively maintained as of 2026-07-06 with recent release history and stable production status.
Requires Python 3.10 or later.
License in practice
MIT license is permissive; you can use, modify, and distribute this package freely in commercial and private projects with minimal restrictions.
Quickstart
pip install genson
from genson import SchemaBuilder
builder = SchemaBuilder()
builder.add_object({"name": "Alice", "age": 30})
builder.add_object({"name": "Bob"})
schema = builder.to_schema()
print(schema)Verify before relying
- Whether the package handles deeply nested or very large JSON structures efficiently.
- Performance characteristics when merging hundreds or thousands of schemas.
- Extent of customization available through extensibility for non-standard merging behavior.
Package facts
| License | MIT permissive |
| Python support | Supports the current Python release >=3.10 |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | None |
| Maintenance | Actively maintained 39 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 19,370,440 / month, #1,068 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 5 - Production/StableEnvironment :: ConsoleIntended Audience :: DevelopersLicense :: OSI Approved :: MIT LicenseNatural Language :: EnglishOperating System :: OS IndependentProgramming Language :: PythonProgramming Language :: Python :: 3Programming Language :: Python :: 3.10Programming Language :: Python :: 3.11Programming Language :: Python :: 3.12Programming Language :: Python :: 3.13Programming Language :: Python :: 3.14Topic :: File Formats :: JSON :: JSON SchemaTopic :: Software Development :: Code GeneratorsTopic :: Software Development :: Libraries :: Python ModulesTopic :: Utilities |
Evidence: genson-1.4.0-py3-none-any.whl
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See also warchant_dc_schema · marshmallow-jsonschema · jsonmerge · jschon · jsonschema-typed-v2 · dydantic · jsonschema-pydantic-converter · jsonschema2md · json-schema-for-humans · json-strong-typing