Workers and performance

Engine execution

The default engineMode="main-thread" evaluates the form engine on the UI thread. Use engineMode="worker" to move engine evaluation into the packaged module worker when Web Workers are available:

Code
<FormRenderer schema={schema} engineMode="worker" />

Vite supports the static module-worker pattern used by the package and emits the worker during a production build. The maintained Vite starter excludes form0-react from dependency optimization so this worker remains available.

The public FormRenderer API does not accept a custom worker URL or worker factory. Applications using another bundler should confirm that it supports new Worker(new URL("./worker.js", import.meta.url), { type: "module" }); otherwise use the default main-thread mode.

If the browser has no Worker support, the binding falls back to main-thread execution.

React store mode

engineStoreMode="snapshot" clones the engine snapshot into React state and is the default. engineStoreMode="selector" uses field subscriptions to reduce broad rerenders.

Treat selector mode as an optimization: verify field errors, navigation summaries, repeatable sections, and submission behavior in the target application before adopting it.