Formisch is an open-source, framework-agnostic form library designed to help developers build performant and type-safe forms across modern JavaScript frameworks. It provides a unified core that works with frameworks like React, Vue, and Svelte while remaining native to each environment through framework-specific integrations.

At its core, Formisch is a schema-based system powered by Valibot, which acts as the single source of truth for both validation and type inference. This allows developers to define form structure and validation rules in one place while automatically generating strongly typed form data and editor autocompletion.

A key design principle of Formisch is modularity. Its API is structured so that only the imported features are included in the final bundle, resulting in very small bundle sizes (starting around 2.5 kB). This makes it suitable for performance-sensitive applications and modern frontend architectures.

Formisch uses a headless design, meaning it does not impose any UI components or styling. Developers can connect it to their own components or design systems, giving full control over presentation while the library handles form state, validation, and logic.

The library also focuses on fine-grained reactivity. Built on signal-based updates, it ensures that only the necessary parts of the UI re-render when form state changes, improving performance compared to traditional form libraries that trigger full component updates.

Formisch supports advanced form capabilities such as deeply nested data structures, dynamic field arrays, and programmatic control over form state through methods like validation, reset, and submission handling. It wraps native HTML form behavior while extending it with structured state management and validation flows.

The project is open-source under the MIT license and is developed publicly, with contributions from the community. It is positioned as a lightweight, modern alternative to traditional form libraries, emphasizing type safety, performance, and flexibility across frameworks.

Key features include:

• Framework-agnostic core with native integrations for React, Vue, and Svelte
• Schema-based validation using Valibot
• Full TypeScript type safety with inferred form types
• Modular API with small bundle size (~2.5 kB starting size)
• Headless design for full UI customization
• Fine-grained reactivity using signals for performance
• Support for nested data structures and dynamic field arrays
• Programmatic control via hooks, methods, and composables
• Open-source under MIT license

Common use cases include:

• Building forms in modern frontend frameworks
• Creating type-safe input validation systems
• Managing complex or nested form state
• Developing reusable form components and design systems
• Optimizing frontend performance in form-heavy applications

Formisch is developed as an open-source project led by Fabian Hiller, with the goal of creating a lightweight, framework-agnostic platform for building fast and type-safe forms.