Ajv is a popular JSON Schema validator used for data validation in JavaScript applications. It supports the latest JSON Schema draft compatible with many other validators including tv4, draft-js-validator, and z-schema. Ajv has a small and fast implementation, making it suitable for use in both frontend and backend applications. It also supports asynchronous validation and offers many features for generating custom errors and dialects.
Zod is a lightweight TypeScript schema validation library that is designed to make it easy to validate and sanitize complex input data. It provides a simple and intuitive syntax for defining a schema that can be used to validate objects, as well as a performant runtime validation engine that can validate data at runtime.
Ajv has been around for longer and is widely used in the JavaScript community. It has a large user base and is considered one of the most popular JSON schema validators. Zod, on the other hand, is a relatively newer library but has gained popularity due to its simplicity and developer-friendly API.
Size
Zod is a lightweight library with a smaller bundle size compared to Ajv. It focuses on providing a minimalistic and efficient validation solution. Ajv, while more feature-rich, has a larger codebase and may result in a larger bundle size.
Validation Features
Both Ajv and Zod provide comprehensive validation features. Ajv supports JSON Schema draft-07 and has extensive support for JSON Schema validation keywords. It also offers advanced features like asynchronous validation and custom keyword definitions. Zod, on the other hand, provides a simpler and more intuitive API for defining and validating data structures. It offers a fluent interface and supports runtime type checking.
Developer Experience
Zod focuses on providing a great developer experience with a clean and intuitive API. It offers strong typing support for TypeScript and provides detailed error messages. Ajv, while powerful, has a steeper learning curve and may require more configuration for advanced use cases. It also has good TypeScript support but may not be as developer-friendly as Zod.
Extensibility
Ajv provides extensive support for custom keyword definitions, allowing developers to extend its functionality. It has a large ecosystem of plugins and integrations. Zod, on the other hand, is more opinionated and does not provide as much flexibility for customizations. It focuses on providing a simple and straightforward validation solution.
Maintenance
Both Ajv and Zod are actively maintained by their respective communities. Ajv has been around for a longer time and has a more established maintenance history. Zod, being a newer library, may have a smaller community but is actively maintained and has regular updates.
