# Ajv JSON schema validator
The fastest JSON validator for Node.js and browser.
Supports JSON Schema draft-04/06/07/2019-09/2020-12 ([draft-04 support](https://ajv.js.org/json-schema.html#draft-04) requires ajv-draft-04 package) and JSON Type Definition [RFC8927](https://datatracker.ietf.org/doc/rfc8927/).
[](https://github.com/ajv-validator/ajv/actions?query=workflow%3Abuild)
[](https://www.npmjs.com/package/ajv)
[](https://www.npmjs.com/package/ajv)
[](https://coveralls.io/github/ajv-validator/ajv?branch=master)
[](https://simplex.chat/contact#/?v=1-2&smp=smp%3A%2F%2Fu2dS9sG8nMNURyZwqASV4yROM28Er0luVTx5X1CsMrU%3D%40smp4.simplex.im%2F8KvvURM6J38Gdq9dCuPswMOkMny0xCOJ%23%2F%3Fv%3D1-2%26dh%3DMCowBQYDK2VuAyEAr8rPVRuMOXv6kwF2yUAap-eoVg-9ssOFCi1fIrxTUw0%253D%26srv%3Do5vmywmrnaxalvz6wi3zicyftgio6psuvyniis6gco6bp6ekl4cqj4id.onion&data=%7B%22type%22%3A%22group%22%2C%22groupLinkId%22%3A%224pwLRgWHU9tlroMWHz0uOg%3D%3D%22%7D)
[](https://gitter.im/ajv-validator/ajv)
[](https://github.com/sponsors/epoberezkin)
## Ajv sponsors
[
](https://www.mozilla.org)
[
](https://opencollective.com/ajv)
[
](https://opensource.microsoft.com)[](https://opencollective.com/ajv)[](https://opencollective.com/ajv)
[
](https://retool.com/?utm_source=sponsor&utm_campaign=ajv)[
](https://tidelift.com/subscription/pkg/npm-ajv?utm_source=npm-ajv&utm_medium=referral&utm_campaign=enterprise)[
](https://github.com/simplex-chat/simplex-chat)[](https://opencollective.com/ajv)
## Contributing
More than 100 people contributed to Ajv, and we would love to have you join the development. We welcome implementing new features that will benefit many users and ideas to improve our documentation.
Please review [Contributing guidelines](./CONTRIBUTING.md) and [Code components](https://ajv.js.org/components.html).
## Documentation
All documentation is available on the [Ajv website](https://ajv.js.org).
Some useful site links:
- [Getting started](https://ajv.js.org/guide/getting-started.html)
- [JSON Schema vs JSON Type Definition](https://ajv.js.org/guide/schema-language.html)
- [API reference](https://ajv.js.org/api.html)
- [Strict mode](https://ajv.js.org/strict-mode.html)
- [Standalone validation code](https://ajv.js.org/standalone.html)
- [Security considerations](https://ajv.js.org/security.html)
- [Command line interface](https://ajv.js.org/packages/ajv-cli.html)
- [Frequently Asked Questions](https://ajv.js.org/faq.html)
## 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 Collective](https://opencollective.com/ajv)
Thank you.
#### Open Collective sponsors
## Performance
Ajv generates code to turn JSON Schemas into super-fast validation functions that are efficient for v8 optimization.
Currently Ajv is the fastest and the most standard compliant validator according to these benchmarks:
- [json-schema-benchmark](https://github.com/ebdrup/json-schema-benchmark) - 50% faster than the second place
- [jsck benchmark](https://github.com/pandastrike/jsck#benchmarks) - 20-190% faster
- [z-schema benchmark](https://rawgit.com/zaggino/z-schema/master/benchmark/results.html)
- [themis benchmark](https://cdn.rawgit.com/playlyfe/themis/master/benchmark/results.html)
Performance of different validators by [json-schema-benchmark](https://github.com/ebdrup/json-schema-benchmark):
[](https://github.com/ebdrup/json-schema-benchmark/blob/master/README.md#performance)
## Features
- Ajv implements JSON Schema [draft-06/07/2019-09/2020-12](http://json-schema.org/) standards (draft-04 is supported in v6):
- all validation keywords (see [JSON Schema validation keywords](https://ajv.js.org/json-schema.html))
- [OpenAPI](https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.3.md) extensions:
- NEW: keyword [discriminator](https://ajv.js.org/json-schema.html#discriminator).
- keyword [nullable](https://ajv.js.org/json-schema.html#nullable).
- full support of remote references (remote schemas have to be added with `addSchema` or compiled to be available)
- support of recursive references between schemas
- correct string lengths for strings with unicode pairs
- JSON Schema [formats](https://ajv.js.org/guide/formats.html) (with [ajv-formats](https://github.com/ajv-validator/ajv-formats) plugin).
- [validates schemas against meta-schema](https://ajv.js.org/api.html#api-validateschema)
- NEW: supports [JSON Type Definition](https://datatracker.ietf.org/doc/rfc8927/):
- all keywords (see [JSON Type Definition schema forms](https://ajv.js.org/json-type-definition.html))
- meta-schema for JTD schemas
- "union" keyword and user-defined keywords (can be used inside "metadata" member of the schema)
- supports [browsers](https://ajv.js.org/guide/environments.html#browsers) and Node.js 10.x - current
- [asynchronous loading](https://ajv.js.org/guide/managing-schemas.html#asynchronous-schema-loading) of referenced schemas during compilation
- "All errors" validation mode with [option allErrors](https://ajv.js.org/options.html#allerrors)
- [error messages with parameters](https://ajv.js.org/api.html#validation-errors) describing error reasons to allow error message generation
- i18n error messages support with [ajv-i18n](https://github.com/ajv-validator/ajv-i18n) package
- [removing-additional-properties](https://ajv.js.org/guide/modifying-data.html#removing-additional-properties)
- [assigning defaults](https://ajv.js.org/guide/modifying-data.html#assigning-defaults) to missing properties and items
- [coercing data](https://ajv.js.org/guide/modifying-data.html#coercing-data-types) to the types specified in `type` keywords
- [user-defined keywords](https://ajv.js.org/guide/user-keywords.html)
- additional extension keywords with [ajv-keywords](https://github.com/ajv-validator/ajv-keywords) package
- [\$data reference](https://ajv.js.org/guide/combining-schemas.html#data-reference) to use values from the validated data as values for the schema keywords
- [asynchronous validation](https://ajv.js.org/guide/async-validation.html) of user-defined formats and keywords
## Install
To install version 8:
```
npm install ajv
```
## Getting started
Try it in the Node.js REPL: https://runkit.com/npm/ajv
In JavaScript:
```javascript
// or ESM/TypeScript import
import Ajv from "ajv"
// Node.js require:
const Ajv = require("ajv")
const ajv = new Ajv() // options can be passed, e.g. {allErrors: true}
const schema = {
type: "object",
properties: {
foo: {type: "integer"},
bar: {type: "string"},
},
required: ["foo"],
additionalProperties: false,
}
const data = {
foo: 1,
bar: "abc",
}
const validate = ajv.compile(schema)
const valid = validate(data)
if (!valid) console.log(validate.errors)
```
Learn how to use Ajv and see more examples in the [Guide: getting started](https://ajv.js.org/guide/getting-started.html)
## Changes history
See [https://github.com/ajv-validator/ajv/releases](https://github.com/ajv-validator/ajv/releases)
**Please note**: [Changes in version 8.0.0](https://github.com/ajv-validator/ajv/releases/tag/v8.0.0)
[Version 7.0.0](https://github.com/ajv-validator/ajv/releases/tag/v7.0.0)
[Version 6.0.0](https://github.com/ajv-validator/ajv/releases/tag/v6.0.0).
## Code of conduct
Please review and follow the [Code of conduct](./CODE_OF_CONDUCT.md).
Please report any unacceptable behaviour to ajv.validator@gmail.com - it will be reviewed by the project team.
## Security contact
To report a security vulnerability, please use the
[Tidelift security contact](https://tidelift.com/security).
Tidelift will coordinate the fix and disclosure. Please do NOT report security vulnerabilities via GitHub issues.
## Open-source software support
Ajv is a part of [Tidelift subscription](https://tidelift.com/subscription/pkg/npm-ajv?utm_source=npm-ajv&utm_medium=referral&utm_campaign=readme) - it provides a centralised support to open-source software users, in addition to the support provided by software maintainers.
## License
[MIT](./LICENSE)
================================================
FILE: benchmark/jtd.js
================================================
/* eslint-disable no-empty */
/* eslint-disable no-console */
const Ajv = require("ajv/dist/jtd")
const Benchmark = require("benchmark")
const jtdValidationTests = require("../spec/json-typedef-spec/tests/validation.json")
const ajv = new Ajv()
const suite = new Benchmark.Suite()
const tests = []
for (const testName in jtdValidationTests) {
const {schema, instance, errors} = jtdValidationTests[testName]
const valid = errors.length === 0
if (!valid) continue
tests.push({
validate: ajv.compile(schema),
serialize: ajv.compileSerializer(schema),
parse: ajv.compileParser(schema),
data: instance,
json: JSON.stringify(instance),
})
}
// suite.add("JTD test suite: compiled JTD serializers", () => {
// for (const test of tests) {
// test.serialize(test.data)
// }
// })
// suite.add("JTD test suite: JSON.stringify", () => {
// for (const test of tests) {
// JSON.stringify(test.data)
// }
// })
const testSchema = {
definitions: {
obj: {
properties: {
foo: {type: "string"},
bar: {type: "int8"},
},
},
},
properties: {
a: {ref: "obj"},
},
optionalProperties: {
b: {ref: "obj"},
},
}
const testData = {
a: {
foo: "foo1",
bar: 1,
},
b: {
foo: "foo2",
bar: 2,
},
}
// const serializer = ajv.compileSerializer(testSchema)
// suite.add("test data: compiled JTD serializer", () => serializer(testData))
// suite.add("test data: JSON.stringify", () => JSON.stringify(testData))
suite.add("JTD test suite: compiled JTD parsers", () => {
for (const test of tests) {
test.parse(test.json)
}
})
suite.add("JTD test suite: JSON.parse", () => {
for (const test of tests) {
JSON.parse(test.json)
}
})
suite.add("JTD test suite: JSON.parse + validate", () => {
for (const test of tests) {
JSON.parse(test.json)
}
})
const validTestData = JSON.stringify(testData)
const invalidTestData = JSON.stringify({
a: {
foo: "foo1",
bar: "1",
},
b: {
foo: "foo2",
bar: 2,
},
})
const parse = ajv.compileParser(testSchema)
const validate = ajv.compile(testSchema)
suite.add("valid test data: compiled JTD parser", () => parse(validTestData))
suite.add("valid test data: JSON.parse", () => JSON.parse(validTestData))
suite.add("valid test data: JSON.parse + validate", () => validate(JSON.parse(validTestData)))
suite.add("invalid test data: compiled JTD parser", () => parse(invalidTestData))
suite.add("invalid test data: JSON.parse", () => JSON.parse(invalidTestData))
suite.add("invalid test data: JSON.parse + validate", () => validate(JSON.parse(invalidTestData)))
console.log()
suite
.on("cycle", (event) => console.log(String(event.target)))
.on("complete", function () {
// eslint-disable-next-line no-invalid-this
console.log('The fastest is "' + this.filter("fastest").map("name") + '"')
})
.run({async: true})
================================================
FILE: benchmark/package.json
================================================
{
"private": true,
"devDependencies": {
"benchmark": "^2.1.4"
}
}
================================================
FILE: bower.json
================================================
{
"name": "ajv",
"description": "Another JSON Schema Validator",
"main": "bundle/ajv.min.js",
"authors": ["Evgeny Poberezkin"],
"license": "MIT",
"keywords": ["JSON", "schema", "validator"],
"homepage": "https://github.com/ajv-validator/ajv",
"moduleType": ["amd", "globals", "node"],
"ignore": ["node_modules", "bower_components", "spec"]
}
================================================
FILE: docs/.vuepress/components/Button.vue
================================================
{{ data.tagline || $description || 'Welcome to your VuePress site' }}
{{ feature.details }}
←
{{ prev.title || prev.path }}
// Make sure to add code blocks to your code group
{{ getMsg() }}
](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 (RFC8927)](https://datatracker.ietf.org/doc/rfc8927/).
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.
================================================
FILE: docs/news/2020-12-15-ajv-version-7-released.md
================================================
---
news: true
title: Ajv version 7 is released!
date: 2020-12-15
---
Ajv version 7 has these new features:
- support of JSON Schema draft-2019-09 features: unevaluatedProperties and unevaluatedItems, dynamic recursive references and other additional keywords.
- 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 and to allow code optimization (compiled schema code size is reduced by more than 10%).
- 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. [ajv-keywords](https://github.com/ajv-validator/ajv-keywords) package was updated to use the new API (in [v4.0.0](https://github.com/ajv-validator/ajv-keywords/releases/tag/v4.0.0))
- schemas are compiled to ES6 code (ES5 code generation is also 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 [Ajv v6](https://github.com/ajv-validator/ajv/tree/v6) that will be supported until 02/28/2021).
- all formats are separated to ajv-formats package - they have to be explicitly added if you use them.
See [release notes](https://github.com/ajv-validator/ajv/releases/tag/v7.0.0) for the details.
To install the new version:
```bash
npm install ajv
```
See [Getting started](/guide/getting-started.md) for code examples.
================================================
FILE: docs/news/2021-03-07-ajv-supports-json-type-definition.md
================================================
---
news: true
title: Ajv supports JSON Type Definition
date: 2021-03-07
---
JSON Type Definition (JTD) is a new specification for defining JSON structures that is very simple to use, comparing with JSON Schema, less error prone, and it is published as [RFC8927](https://datatracker.ietf.org/doc/rfc8927/).
See Choosing schema language for a detailed comparison between JSON Schema and JSON Type definition and informal specification.
In addition to validation, Ajv also supports:
- generation of [serializers](/api.html#jtd-serialize) and [parsers](/api.html#jtd-parse) from JTD schemas/ This is more efficient than native JSON serialization/parsing - you can combine JSON string parsing and validation in one function call.
- utility type [JTDSchemaType](/guide/typescript.html#utility-types-for-schemas) to convert your data type to the type of JTD schema and [JTDDataType](/guide/typescript.html#utility-type-for-jtd-data-type) to convert the type of schema to the type of data.
================================================
FILE: docs/news/2021-03-27-ajv-version-8-released.md
================================================
---
news: true
title: Ajv version 8 is released!
date: 2021-03-27
---
Ajv version 8 has these new features:
- support of JSON Schema draft-2020-12: prefixItems keyword and changed semantics of items keyword, dynamic recursive references.
- OpenAPI discriminator keyword.
- improved JSON Type Definition support:
- errors consistent with JTD specification.
- error objects with additional properties to simplify error handling
- internationalized error messages with [ajv-i18n](/packages/ajv-i18n)
- TypeScript: support type unions in [JSONSchemaType](/guide/typescript.html#type-safe-unions)
See [release notes](https://github.com/ajv-validator/ajv/releases/tag/v8.0.0) for the details.
To install the new version:
```bash
npm install ajv
```
See [Getting started](/guide/getting-started.md) for code examples.
================================================
FILE: docs/news/2021-04-24-ajv-online-event.md
================================================
---
news: true
title: "Ajv online event - May 20, 10am PT / 6pm UK"
date: 2021-04-24
more: false
---
We will talk about:
- new features of Ajv version 8.
- the improvements sponsored by Mozilla's MOSS grant.
- how Ajv is used in JavaScript applications.
Speakers:
- [Evgeny Poberezkin](https://github.com/epoberezkin), the creator of Ajv.
- [Mehan Jayasuriya](https://github.com/mehan), Program Officer at Mozilla Foundation, leading the [MOSS](https://www.mozilla.org/en-US/moss/) and other programs investing in the open source and community ecosystems.
- [Matteo Collina](https://github.com/mcollina), Technical Director at NearForm and Node.js Technical Steering Committee member, creator of Fastify web framework.
- [Kin Lane](https://github.com/kinlane), Chief Evangelist at Postman. Studying the tech, business & politics of APIs since 2010. Presidential Innovation Fellow during the Obama administration.
- [Ulysse Carion](https://github.com/ucarion), the creator of JSON Type Definition specification.
[Gajus Kuizinas](https://github.com/gajus) will host the event.
Please [register here](https://us02web.zoom.us/webinar/register/4216192074976/WN_erJ_t4ICTHOnGC1SOybNnw).
================================================
FILE: docs/news/2021-05-24-ajv-online-event-video.md
================================================
---
news: true
title: Ajv online event video uploaded
date: 2021-05-24
more: false
---
Huge thanks to everybody who joined, and to the speakers! The video of the event is [available on YouTube](https://www.youtube.com/watch?v=KxSKqXEBB7A).
================================================
FILE: docs/news/2021-07-22-ajv-microsoft-foss-fund-award.md
================================================
---
news: true
title: Microsoft FOSS award
date: 2021-07-22
more: false
---
Ajv was awarded a sponsorship from [Microsoft FOSS fund](https://github.com/microsoft/foss-fund/blob/main/README.md#2021) - huge thanks to Microsoft and the engineers who voted to support Ajv development.
This award will contribute to a long term maintenance of Ajv.
================================================
FILE: docs/news/README.md
================================================
---
newsIndex: true
editLink: false
---
# Ajv News