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Modyra

Compared with JSON Forms

JSON Forms is the closest neighbour to Modyra’s contract mode: it also renders a form from data rather than from component code, and it also ships bindings for more than one framework. This page is here to help you decide, and it says where JSON Forms is the better answer.

Snapshot date: 2026-08-22. Both projects move; re-read the sources before quoting this page.

The contracts differ in what they can say

Section titled “The contracts differ in what they can say”

JSON Forms speaks JSON Schema: the form is a data schema plus a UI schema, and validation is what AJV can express over that schema. Modyra’s Dynamic Form Contract is a smaller, form-shaped vocabulary: field kinds, validator options, layout nodes and rule operators — bounded on purpose, so that a document from an untrusted source can be parsed strictly and rejected or reported before anything renders.

Aspect JSON Forms Modyra
Contract format JSON Schema + UI schema Dynamic Form Contract — fields, layout, rules, validators as form-shaped data
Validation AJV over the data schema; custom rules need code Validator options in the contract; async, cross-field and server validation are engine features, not document extensions
Untrusted documents The document is a schema — the power and the exposure of JSON Schema Strict mode refuses a document with any diagnostic; lenient mode reports and keeps what parsed
Frameworks React, Angular, Vue bindings Angular, Lit and framework-free renderers; React, Vue, Solid, Preact, Svelte headless adapters
Lifecycle (drafts, undo, async cancellation) Not part of the model In the engine, so contract-driven forms get them too
Producers Anything that emits JSON Schema TypeScript, the Rust and Java SDKs, and Studio — which can also export ordinary source instead of the contract
Maturity Long production history, EclipseSource stewardship Younger; core and widgets versioned under a compatibility policy, adapters below 1.0

Choose JSON Forms if…

Section titled “Choose JSON Forms if…”
  • Your source of truth already is JSON Schema — existing schemas, an OpenAPI document, a code generator that emits them.
  • You want AJV’s validation semantics and its ecosystem of formats and keywords.
  • React, Angular or Vue covers your surfaces.

Choose Modyra if…

Section titled “Choose Modyra if…”
  • The form must survive being produced by something you do not control — a service, a CMS, a model — and be parsed strictly before it renders.
  • You need the lifecycle with the form, not beside it: drafts, undo, cancellable async validation.
  • The same form has to reach frameworks outside React/Angular/Vue, or no framework at all.

See also

Section titled “See also”