Vest — form validation written like unit tests
Documentation · Async race demo · Getting started
Vest runs the tests for the field or step that changed and keeps the results for everything else. When async checks overlap, only the latest result can update the suite.
Vest validates what changed, remembers what already passed, and prevents stale async validation results.
The validation rules read like unit tests. The stateful runtime is what makes Vest different.
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Why Vest?
- Incremental execution: Validate a field, group, or step without rerunning everything.
- Retained validation state: A focused run updates part of the existing result instead of replacing it.
- Race-safe async: Track pending work, cancel obsolete requests, and ignore stale completions.
- Real workflow primitives: Model dependent fields, conditional sections, warnings, optional values, groups, and dynamic lists.
- Client and server continuity: Run statelessly on the server and resume full validation state in the browser.
- Framework independence: Use the same suite with React, Vue, Svelte, Angular, vanilla JavaScript, or Node.js.
- TypeScript and schemas: Infer typed inputs and parsed outputs with Enforce schemas.
- Standard Schema interoperability: Pass suites and Enforce rules to compatible tools while keeping
run() and runStatic() as Vest's execution APIs.
- Familiar, testable rules: Keep business validation outside UI components in suites that are easy to unit-test.
Where Vest fits
Layer
Responsibility
Typical tools
Form state
Values, registration, touched state, submission
React Hook Form, Formik
Data boundary
Parse and protect a complete payload
Zod, Valibot, Ajv, Enforce schemas
Validation state
Decide what runs now, retain results, coordinate async work
Vest
These layers are complementary. A common architecture uses a form manager for input mechanics, Vest for progressive interaction, and a schema validator for the final submitted boundary.
Where Vest works well
Vest works well for:
- async username, email, inventory, coupon, or eligibility checks;
- onboarding and multi-step workflows;
- linked fields and cross-field business rules;
- warnings that should not block submission;
- optional and conditional sections;
- dynamic lists of travelers, products, or addresses;
- rules shared between browser and server;
- SSR workflows that should not validate everything twice.
For a trivial synchronous form or a one-shot API parse, native HTML validation or a schema validator may be all you need.
Installation
npm i vest
Start here
Contributing
Contributions are welcome. See CONTRIBUTING.md.