Ajv vs Zod
Which should you use? A side-by-side look at what each one does, who it suits, what it costs, how hard it is to set up, and where each falls short.
Open source · MIT
A fast library that checks whether JSON data matches a schema, for Node.js and browsers.
Open source · MIT
TypeScript-first library for validating data at runtime and inferring static types from the same schema.
The short answer
Choose Ajv if you need…
- Node.js developers validating API request or response bodies
- Front-end developers validating form or config data in the browser
- Teams already writing JSON Schema who need a standards-based checker
- Projects that need draft-04 support (via the separate ajv-draft-04 package)
Choose Zod if you need…
- TypeScript developers who want runtime checks that match their static types
- Teams validating API request or response data in TypeScript projects
- Developers who want one schema definition instead of separate types and validators
Side-by-side
| Ajv | Zod | |
|---|---|---|
| Type | Library | Library |
| Price | Free and open source | Free and open source |
| Licence | MIT | MIT |
| GitHub stars | 14.9k | 44.2k |
| Setup difficulty | Intermediate | Beginner |
| How you get it | Install with a package manager | Install with a package manager |
| Main language | TypeScript | TypeScript |
| Last code update | 2 months ago | 6 days ago |
What each one is
Ajv
Ajv is a JavaScript/TypeScript library that checks JSON data against a schema, such as confirming a form submission or API request has the required fields and types. It supports JSON Schema drafts 04, 06, 07, 2019-09 and 2020-12, plus JSON Type Definition (RFC 8927). The README describes it as fast, and it generates validation code from schemas to achieve this.
Zod
Zod is a TypeScript library for defining schemas that check whether data has the expected shape, such as form input or API responses. You describe the shape once, and Zod both validates values at runtime and gives you a TypeScript type that matches it. The README provided is truncated and only points to the package, so details beyond that are limited here.
Best for
Ajv
- Node.js developers validating API request or response bodies
- Front-end developers validating form or config data in the browser
- Teams already writing JSON Schema who need a standards-based checker
- Projects that need draft-04 support (via the separate ajv-draft-04 package)
Zod
- TypeScript developers who want runtime checks that match their static types
- Teams validating API request or response data in TypeScript projects
- Developers who want one schema definition instead of separate types and validators
Strengths
Ajv
- The README claims it is the fastest JSON schema validator and cites third-party benchmarks
- Supports multiple JSON Schema drafts and JSON Type Definition
- MIT licensed with a large community (over 100 contributors per the README)
Zod
- Schemas produce both runtime validation and static type inference
- MIT licensed and widely starred (about 44k stars at time of metadata)
- Actively maintained, with a recent release (v4.6.7) and a recent push
Not ideal for
Ajv
- People who are new to programming and just want a simple form library, since it requires writing schemas
- Projects that need a non-JavaScript runtime, since the README only mentions Node.js and browsers
- Users who only need to check a few values by hand, where a simple function would be enough
Zod
- Projects not using TypeScript, since the library is described as TypeScript-first and the README excerpt gives no JavaScript-only guidance
- Readers needing a no-code tool, because this is a code library that requires writing schemas
Trade-offs
Ajv
- Draft-04 support requires an extra package, so setup is not one step for older schemas
- The README is short and points to an external website for most documentation
- Performance claims come from the project's own README citing older benchmarks
Zod
- The README excerpt was truncated, so API details and setup specifics could not be verified here
- Being TypeScript-first means its main value depends on using TypeScript
Getting started
Zod
Clone the repository
git clone https://github.com/colinhacks/zodFrequently asked questions
What is the difference between Ajv and Zod?
Ajv: A fast library that checks whether JSON data matches a schema, for Node.js and browsers. Zod: TypeScript-first library for validating data at runtime and inferring static types from the same schema. Ajv suits node.js developers validating api request or response bodies, while Zod suits typescript developers who want runtime checks that match their static types.
Are Ajv and Zod free?
Ajv: Free and open source. Zod: Free and open source.
Which is easier to set up, Ajv or Zod?
Zod is easier to get started with (rated beginner); Ajv is rated intermediate and usually needs more setup.
Is Ajv or Zod more popular?
Zod has more GitHub stars (44.2k) than Ajv (14.9k). Popularity isn't the same as fit — check which one matches your use case above.
What are other alternatives to Ajv and Zod?
Other options people compare them with include Formily, Pydantic, SQLModel, Yup, ts-pattern.
Keep comparing
Built from our catalogue entries for both products: open-source details come from each project's README (AI-assisted, refreshed weekly) and GitHub data; AI-tool details are editorial. Spotted something wrong? Let us know from either product's page.