# Comparison

Formisch is one of several form libraries available for Svelte. The two most common alternatives are [Superforms](https://superforms.rocks) and [TanStack Form](https://tanstack.com/form/latest). This page is meant as a quick reference for picking the right tool.

## At a glance

|                        | **Formisch**                            | Superforms                           | TanStack Form                           |
| ---------------------- | --------------------------------------- | ------------------------------------ | --------------------------------------- |
| Type source            | Inferred from schema                    | Inferred from schema                 | Inferred from `defaultValues`           |
| Validation location    | Defined in schema                       | Defined in schema                    | Per-validator config                    |
| Validation timing      | Form-wide `validate` / `revalidate`     | Configurable per form / event        | Per-validator trigger                   |
| Async validation       | Built-in via schema                     | Built-in (client + server)           | Built-in `isValidating`                 |
| Reactivity scope       | Fine-grained per rune                   | Per Svelte store / rune              | Per subscription                        |
| Schema libraries       | Valibot                                 | Zod, Valibot, Yup, ArkType, …        | Standard Schema                         |
| Server integration     | Client-only (SvelteKit support planned) | First-class (SvelteKit form actions) | Client-only                             |
| Bundle size (min+gzip) | From ~2.5 kB                            | ~20 kB                               | ~15 kB                                  |
| Framework support      | React, Preact, Solid, Svelte, Vue, Qwik | Svelte / SvelteKit                   | React, Vue, Solid, Svelte, Lit, Angular |

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](https://valibot.dev) 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 <Link href="/svelte/guides/installation/">installation</Link> guide and start building by <Link href="/svelte/guides/define-your-form/">defining your form</Link>.