Ajv: Another JSON Schema Validator

The fastest JSON Schema validator for Node.js and browser. Supports draft-04/06/07.

Ajv v7 beta is released

Ajv version 7.0.0-beta.0 is released with these changes:

• to reduce the mistakes in JSON schemas and unexpected validation results, strict mode is added - it prohibits ignored or ambiguous JSON Schema elements.
• to make code injection from untrusted schemas impossible, code generation is fully re-written to be safe.
• to simplify Ajv extensions, the new keyword API that is used by pre-defined keywords is available to user-defined keywords - it is much easier to define any keywords now, especially with subschemas.
• schemas are compiled to ES6 code (ES5 code generation is supported with an option).
• to improve reliability and maintainability the code is migrated to TypeScript.

Please note:

• the support for JSON-Schema draft-04 is removed - if you have schemas using "id" attributes you have to replace them with "$id" (or continue using version 6 that will be supported until 02/28/2021).
• all formats are separated to ajv-formats package - they have to be explicitely added if you use them.

See release notes for the details.

To install the new version:

npm install ajv@beta

See Getting started with v7 for code example.

Mozilla MOSS grant and OpenJS Foundation

Ajv has been awarded a grant from Mozilla’s Open Source Support (MOSS) program in the “Foundational Technology” track! It will sponsor the development of Ajv support of JSON Schema version 2019-09 and of JSON Type Definition.

Ajv also joined OpenJS Foundation – having this support will help ensure the longevity and stability of Ajv for all its users.

This blog post has more details.

I am looking for the long term maintainers of Ajv – working with ReadySet, also sponsored by Mozilla, to establish clear guidelines for the role of a "maintainer" and the contribution standards, and to encourage a wider, more inclusive, contribution from the community.

Please sponsor Ajv development

Since I asked to support Ajv development 40 people and 6 organizations contributed via GitHub and OpenCollective - this support helped receiving the MOSS grant!

Your continuing support is very important - the funds will be used to develop and maintain Ajv once the next major version is released.

Please sponsor Ajv via:

• GitHub sponsors page (GitHub will match it)
• Ajv Open Collective️

Thank you.

Open Collective sponsors

Using version 6

JSON Schema draft-07 is published.

Ajv version 6.0.0 that supports draft-07 is released. It may require either migrating your schemas or updating your code (to continue using draft-04 and v5 schemas, draft-06 schemas will be supported without changes).

Please note: To use Ajv with draft-06 schemas you need to explicitly add the meta-schema to the validator instance:

ajv.addMetaSchema(require('ajv/lib/refs/json-schema-draft-06.json'));

To use Ajv with draft-04 schemas in addition to explicitly adding meta-schema you also need to use option schemaId:

var ajv = new Ajv({schemaId: 'id'});
// If you want to use both draft-04 and draft-06/07 schemas:
// var ajv = new Ajv({schemaId: 'auto'});
ajv.addMetaSchema(require('ajv/lib/refs/json-schema-draft-04.json'));

Contents

• Performance
• Features
• Getting started
• Frequently Asked Questions
• Using in browser
  • Ajv and Content Security Policies (CSP)
• Command line interface
• Validation
  • Keywords
  • Annotation keywords
  • Formats
  • Combining schemas with $ref
  • $data reference
  • NEW: $merge and $patch keywords
  • Defining custom keywords
  • Asynchronous schema compilation
  • Asynchronous validation
• Security considerations
  • Security contact
  • Untrusted schemas
  • Circular references in objects
  • Trusted schemas
  • ReDoS attack
• Modifying data during validation
  • [Filtering