# Ajv: Another JSON Schema Validator
The fastest JSON Schema validator for Node.js and browser. Supports draft-04/06/07.
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## Ajv v7 beta is released
[Ajv version 7.0.0-beta.0](https://github.com/ajv-validator/ajv/tree/v7-beta) is released with these changes:
- to reduce the mistakes in JSON schemas and unexpected validation results, [strict mode](./docs/strict-mode.md) is added - it prohibits ignored or ambiguous JSON Schema elements.
- to make code injection from untrusted schemas impossible, [code generation](./docs/codegen.md) 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](https://github.com/ajv-validator/ajv/releases/tag/v7.0.0-beta.0) for the details.
To install the new version:
```bash
npm install ajv@beta
```
See [Getting started with v7](https://github.com/ajv-validator/ajv/tree/v7-beta#usage) for code example.
## Mozilla MOSS grant and OpenJS Foundation
[
](https://www.mozilla.org/en-US/moss/) [
](https://openjsf.org/blog/2020/08/14/ajv-joins-openjs-foundation-as-an-incubation-project/)
Ajv has been awarded a grant from Mozilla’s [Open Source Support (MOSS) program](https://www.mozilla.org/en-US/moss/) in the “Foundational Technology” track! It will sponsor the development of Ajv support of [JSON Schema version 2019-09](https://tools.ietf.org/html/draft-handrews-json-schema-02) and of [JSON Type Definition](https://tools.ietf.org/html/draft-ucarion-json-type-definition-04).
Ajv also joined [OpenJS Foundation](https://openjsf.org/) – having this support will help ensure the longevity and stability of Ajv for all its users.
This [blog post](https://www.poberezkin.com/posts/2020-08-14-ajv-json-validator-mozilla-open-source-grant-openjs-foundation.html) has more details.
I am looking for the long term maintainers of Ajv – working with [ReadySet](https://www.thereadyset.co/), 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](https://github.com/sponsors/epoberezkin)
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](https://github.com/sponsors/epoberezkin) (GitHub will match it)
- [Ajv Open Collective️](https://opencollective.com/ajv)
Thank you.
#### Open Collective sponsors
## Using version 6
[JSON Schema draft-07](http://json-schema.org/latest/json-schema-validation.html) is published.
[Ajv version 6.0.0](https://github.com/ajv-validator/ajv/releases/tag/v6.0.0) 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:
```javascript
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:
```javascript
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](#performance)
- [Features](#features)
- [Getting started](#getting-started)
- [Frequently Asked Questions](https://github.com/ajv-validator/ajv/blob/master/FAQ.md)
- [Using in browser](#using-in-browser)
- [Ajv and Content Security Policies (CSP)](#ajv-and-content-security-policies-csp)
- [Command line interface](#command-line-interface)
- Validation
- [Keywords](#validation-keywords)
- [Annotation keywords](#annotation-keywords)
- [Formats](#formats)
- [Combining schemas with $ref](#ref)
- [$data reference](#data-reference)
- NEW: [$merge and $patch keywords](#merge-and-patch-keywords)
- [Defining custom keywords](#defining-custom-keywords)
- [Asynchronous schema compilation](#asynchronous-schema-compilation)
- [Asynchronous validation](#asynchronous-validation)
- [Security considerations](#security-considerations)
- [Security contact](#security-contact)
- [Untrusted schemas](#untrusted-schemas)
- [Circular references in objects](#circular-references-in-javascript-objects)
- [Trusted schemas](#security-risks-of-trusted-schemas)
- [ReDoS attack](#redos-attack)
- Modifying data during validation
- [Filtering