Validate data with Acanthis

Acanthis is a schema validation library for Dart and Flutter. Describe the data you expect, validate input at runtime, and use the result in your application.

Use it for form fields, API payloads, configuration, or any other data entering your application. Its chainable API is inspired by Zod.

Installation

Version scope

These docs describe the 2.0 codebase, which requires Dart 3.13 or later. Flutter projects need a Flutter SDK with a compatible Dart version. See the migration guide when upgrading from 1.x; check pub.dev for published releases.

Dart

dart pub add acanthis

Flutter

flutter pub add acanthis

Import the library wherever you define a schema:

import 'package:acanthis/acanthis.dart';

The core idea

A schema combines a type with checks. Parsing applies those checks to an input and returns a result.

final email = string().email();
final result = email.tryParse('ada@example.com');

print(result.success); // true
print(result.value); // ada@example.com

Schema methods return new instances, so you can reuse a base schema and extend its checks. Successful validation can preserve input identity; it does not guarantee a deep copy. See input sharing in 2.0.

Choose your next step

Start with a complete example →Define an object, validate input, and handle errors.Find a schema →Browse types, built-in checks, and composition methods.Understand results →Choose a parsing API and work with structured issues.Validate changing input →Update fields in a live session and inspect validation deltas.

More than validation

• Custom rules for application-specific checks, including async work.
• Transformations for converting input into the output you need.
• JSON Schema and OpenAPI exports for supported schemas.
• Seeded mocking for reproducible test data within a documented supported subset.