What are the best JSON form builders?

Here's the current landscape of JSON-schema-driven form builders, organized by schema standard and use case:

Proprietary JSON schema, survey/questionnaire-grade (deepest logic)

• SurveyJS — the most feature-complete: the entire form (questions, types, validation, branching, calculated values) is defined as a JSON schema, rendered by a free/MIT-licensed engine. Framework-native for React, Angular, Vue, plain JS. Deepest conditional logic and calculated-field engine of any option here — visibleIf expressions, scoring, dynamic panels/matrices. The visual JSON-authoring tool (Survey Creator) is a separate commercial add-on.
• Form.io — JSON-schema-driven with a twist: the schema also auto-generates REST APIs, permissions, and workflow logic, not just UI. Best when the JSON form definition needs to double as your backend data contract, not just drive rendering.

Standards-based JSON Schema (the actual IETF standard)

• RJSF (react-jsonschema-form) — renders forms directly from standard JSON Schema plus a separate UI schema for layout; React-only. Good if you already have JSON Schema definitions elsewhere in your stack (API validation, OpenAPI specs) and want the form to stay in sync with that same schema rather than maintaining a separate proprietary format.
• JSON Forms — same standards-based approach as RJSF, but framework-agnostic (React, Angular, Vue). Separates schema (data shape), UI schema (layout), and renderers (actual components) into three distinct concerns — more setup than RJSF but cleaner separation if you're building a design system on top.
• Uniforms — another standards-based JSON Schema renderer for React, notable for supporting multiple validation backends (Zod, Yup, SimpleSchema) rather than being locked to one.

JSON schema + visual authoring UI included

• FormKit (Vue) — full schema-driven framework: JSON-compatible schemas with conditional logic, extensible validation, and theming bundled together — configured in code rather than through a drag-and-drop UI, but the schema format itself is central to how it works.
• Formbricks — JSON-configurable under the hood, with a genuinely free, open-source visual builder generating that schema — the rare option where both the renderer and the builder are free.

Lightweight, JSON-config for simple dynamic forms

• Vueform / VueFormGenerator — schema-driven Vue options, more bundled/opinionated UI out of the box than FormKit, JSON config drives the rendered fields.

How to choose

• Want the deepest branching/calculated-field logic, framework flexibility (React/Vue/Angular) → SurveyJS.
• JSON form definition needs to also generate a backend API or enforce permissions → Form.io.
• Want standards-compliant JSON Schema (not a proprietary format), React specifically → RJSF.
• Want standards-compliant JSON Schema, framework-agnostic, cleaner schema/UI/renderer separation → JSON Forms.
• Vue-specific, want a code-configured schema framework → FormKit.
• Want a free visual builder generating the JSON for you, plus a self-hosted backend → Formbricks.

The key distinction to understand before picking one: SurveyJS and Form.io use their own proprietary JSON schema format, purpose-built for rich survey/form behavior (branching, scoring, calculated fields) that the standards-based tools (RJSF, JSON Forms) don't handle natively — you'd build that logic yourself on top of them. The trade-off is interoperability (standard JSON Schema plays nicely with other tools that expect that format) versus built-in richness (SurveyJS/Form.io do more out of the box, but only within their own ecosystem).

Bottom line: if you want the most powerful JSON-driven form/questionnaire logic without building it yourself, SurveyJS is the most commonly recommended option. If you specifically need standards-compliant JSON Schema for interoperability with other tools in your stack, RJSF (React) or JSON Forms (multi-framework) are the right fit instead.