form/docs/guides/important-defaults.md

id, title

id	title
important-defaults	Important Defaults

Some of these docs may be inaccurate due to an API shift in 0.11.0. If you're interested in helping us fix these issues, please join our Discord and reach out in the #form channel.

Out of the box, TanStack Form is configured with aggressive but sane defaults. Sometimes these defaults can catch new users off guard or make learning/debugging difficult if they are unknown by the user. Keep them in mind as you continue to learn and use TanStack Form:

• Core
  • Validation
    • By default, only touched, dirty fields are validated on blur and submit. This means that if you have a field that is required, it will not show an error until the user has blurred the field (focused and unfocused) or submitted the form. You can change this to include field change events or only the submit event with a form default or on a per field basis with the defaultValidateOn and validateOn options. validatePristine can also be used to validate pristine fields.
    • By default, TanStack async validation will only run if synchronous validation succeeds. This is to prevent unnecessary async validation which usually are powered by network requests.
    • By default, TanStack Form will not validate fields that are not registered. This is to prevent unnecessary validation of fields that are not in the DOM. This can be changed with the validateUnregistered option.
• React
  • Reactivity
    • The useForm hook and form.Form component are not reactive, which means that as any form state changes, they will not rerender. If they did, you would likely run into performance problems very quickly. Instead, use:
      • form.useStore to subscribe and rerender when form state changes. Selectors are supported.
      • form.Subscribe to render a specific sub-tree of UI that is subscribed to the form state. Selectors are supported.
      • form.useField to subscribe to a specific field's state changes.
    • form.Field is reactive to all state changes that happen within a field. This means that as a field's value, error, touched, etc. changes, the component you use it in will rerender. This is a good thing because it means you don't have to worry about manually subscribing to a field's state changes.