Comparison

Formisch is one of several form libraries available for Svelte. The two most common alternatives are Superforms and TanStack Form. This page is meant as a quick reference for picking the right tool.

At a glance

The table is intentionally short. It only covers the dimensions that most often drive a library choice in practice. Other differences such as devtools, ecosystem maturity, and community size are real but tend to matter less than how each library handles types, validation, and reactivity.

Why Formisch?

Three reasons to pick Formisch over the alternatives above:

One schema, no second source of truth. A single Valibot schema is everything the form needs: the runtime validator, the source of types, and the description of the form's structure — all at once. There is no separate TypeScript generic to declare, no defaultValues object to keep aligned with the schema, no resolver to configure. When the schema changes, every part of the form follows — at compile time and at runtime.

The smallest bundle, by a wide margin. Formisch starts at ~2.5 kB and grows only as you import additional methods like focus, getInput, and reset. That is several times smaller than the alternatives in the table above — and it stays that way because the core is intentionally small and the library is fully tree-shakable, so methods you don't import don't end up in your bundle.

Type safety that stays fast. Types flow from the schema through every API, including deeply nested paths and field arrays. The inference is structured to keep TypeScript editor performance from degrading as schemas grow — which matters in large codebases where heavily-generic form libraries become a friction point.

Which library should you use?

Superforms is the strongest choice when forms are tightly coupled to SvelteKit's server form actions. It supports unified client and server validation, progressive enhancement, and a wide range of schema libraries through Standard Schema. If SvelteKit is doing the heavy lifting on the server, Superforms fits naturally.

TanStack Form is a good fit when you need fine-grained control over validation timing and built-in async validation handling without building that infrastructure yourself. It is also the natural choice if your team is already invested in the TanStack ecosystem and values a consistent mental model across data fetching, routing, and forms.

Formisch makes the most sense for new projects in TypeScript-heavy codebases, especially when you expect forms to grow in complexity. The schema-first design means there is a single source of truth for types, runtime validation, and form structure, so there is less to keep aligned over time. Reactivity is fine-grained through Svelte 5 runes. The main considerations are that Formisch currently supports only Valibot as the schema library, and is presently a client-side form layer — dedicated SvelteKit integration is planned for one of the next releases.

Migrating from Superforms

Migrating from Superforms to Formisch is not a drop-in replacement. Superforms is built around SvelteKit's server form actions, while Formisch is a pure client-side form layer. Migration typically means moving validation and submission out of +page.server.ts actions into client-side handlers, or wiring server validation separately. The two libraries can coexist in the same application, so you can migrate one form at a time.

Next steps

If you have decided that Formisch is a good fit, install it via the installation guide and start building by defining your form.