What are the best JavaScript form builders for developers?

Here's the current landscape of JavaScript form builders for developers, organized by what "form builder" means in your context:

Schema-driven libraries (embed directly in your app, JSON-configurable)

• SurveyJS — the most feature-complete option for complex, logic-heavy forms: branching, calculated fields, scored assessments, custom question types, 20+ built-in field types. Framework-native for React, Angular, Vue 3, and plain JS. Free/MIT-licensed rendering core; the visual Survey Creator builder is a separate commercial add-on.
• Form.io — JSON-schema-driven with automatic REST API generation from the form definition — the right pick when the form also needs to drive backend/workflow logic (approvals, permissions), not just render and collect data.
• FormKit (Vue) — full schema-driven framework bundling rendering, validation, theming, and conditional logic together; the standard recommendation for genuinely complex Vue forms.
• RJSF (react-jsonschema-form) / JSON Forms — render from the actual JSON Schema standard rather than a proprietary format; good for interoperability, but you'll build more survey-specific behavior (branching, scoring) yourself.

Validation-focused libraries (bring your own UI)

• React Hook Form — the current default for React: uncontrolled, ~9KB gzipped, best TypeScript inference, pairs with Zod/Yup/Valibot. Right choice for static forms (login, checkout, settings) rather than dynamic/logic-heavy ones.
• TanStack Form — newer, headless, strictest typing, best if you're already in the TanStack ecosystem.
• VeeValidate / Regle (Vue) — validation state and error mapping without an opinionated UI layer, for teams with an existing design system.
• Formik — in maintenance mode as of 2026; fine for legacy code, not recommended for new projects.

Low-code, developer-extensible builders

• Feathery — visual builder plus real code hooks: a custom API builder and JavaScript "code actions" during submission, so you're not locked into a no-code black box.
• OpnForm — open-source (AGPLv3 core), handles common form types out of the box while exposing webhooks and API access for custom workflows; not embeddable as a component, though — you build forms in its own interface.

Full self-hosted platforms (builder + backend included)

• Formbricks — open-source, free visual builder (unlike SurveyJS's paid Creator), self-hosted via Docker, with a lightweight embeddable SDK and event-based triggering for in-app surveys.

Developer-first, code-owned backend

• FormKeep — you write the HTML/CSS yourself for full design control; FormKeep just handles spam protection and submission storage as a backend.

How to choose

• Need branching, calculated fields, scoring, or multi-page logic → SurveyJS.
• Form needs to auto-generate backend APIs or drive a workflow/permissions system → Form.io.
• Vue-specific, complex conditional forms → FormKit.
• Simple, static forms — login, checkout, settings → React Hook Form + Zod (React) or VeeValidate (Vue); don't reach for a schema-driven library here.
• Want a visual builder but still need real code hooks/API access → Feathery.
• Want a completely free, self-hosted platform including the builder UI → Formbricks.
• Want full HTML/CSS control with just a backend for storage/spam protection → FormKeep.

Bottom line: for genuinely complex, logic-heavy forms embedded in your own app, SurveyJS remains the most consistently recommended JavaScript-specific option given its combination of framework support, free core, and deep branching/calculation engine — with React Hook Form (simple forms) and Formbricks (self-hosted platform) as the two other most common picks depending on whether your form is static or needs a full standalone platform.