Validation

ajv

Fast JSON Schema Validator supporting multiple drafts and JSON Type Definition.

Status
Generally available
Last checked
Checked · Oct 5, 2026
License
Open source
Pricing
Free tier
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What it is

AJV (Another JSON Validator) is a JSON schema validator that supports JSON Schema drafts 04, 06, 07, 2019-09, 2020-12, and JSON Type Definition (RFC8927). Written in TypeScript, it is designed for high performance and flexibility, making it suitable for both client-side and server-side validation tasks. AJV is open-source and has a large community of contributors, ensuring regular updates and improvements. It is widely used in the JavaScript ecosystem for validating complex data structures against JSON schemas.

AJV is distinguished by its high performance and comprehensive support for multiple JSON Schema drafts.

When it fits — and when it doesn’t

A good fit for

  • Applications requiring fast JSON validation

    AJV's compiled function approach significantly speeds up validation processes.

  • Projects needing support for multiple JSON Schema drafts

    AJV supports a wide range of JSON Schema drafts, making it versatile for various projects.

Look elsewhere if

  • Developers needing extensive built-in error handling

    AJV's error messages are minimal and may require custom handling.

  • Projects with minimal JSON validation needs

    The complexity and setup of AJV might be overkill for simple validation tasks.

Known weaknesses

Each one links to the public issue, changelog or docs page it came from, where we have one.

  1. 01

    Complexity in advanced use cases

    Users report difficulties when implementing custom keywords and formats.

  2. 02

    Large number of open issues

    Currently has 376 open issues on GitHub.

  3. 03

    Limited built-in error messaging

    Error messages can be cryptic and require additional parsing.

What it does well

  • High performance

    AJV compiles schemas to JavaScript functions to improve validation speed.

  • Wide schema draft support

    Supports JSON Schema drafts 04, 06, 07, 2019-09, 2020-12, and JSON Type Definition.

  • Strong community support

    Over 14,000 stars and 212 contributors on GitHub.

Pricing

Free tier
Yes
Paid from
—
Model
Flat rate
Enterprise plan
No

Pricing last confirmed Sep 27, 2026.

Performance benchmarks

How Fast Is It?

Set up ajv

Setup steps, common gotchas and what to check after 30 days.

Open the setup guide →