# 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/). 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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 Collective️](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)