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<img align="right" alt="Ajv logo" width="160" src="http://epoberezkin.github.io/ajv/images/ajv_logo.png"> # Ajv: Another JSON Schema Validator The fastest JSON Schema validator for Node.js and browser. Supports draft-04/06/07. [](https://travis-ci.org/epoberezkin/ajv) [](https://www.npmjs.com/package/ajv) [](https://www.npmjs.com/package/ajv) [](https://coveralls.io/github/epoberezkin/ajv?branch=master) [](https://greenkeeper.io/) [](https://gitter.im/ajv-validator/ajv) ## 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/epoberezkin/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/epoberezkin/ajv/blob/master/FAQ.md) - [Using in browser](#using-in-browser) - [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 data](#filtering-data) - [Assigning defaults](#assigning-defaults) - [Coercing data types](#coercing-data-types) - API - [Methods](#api) - [Options](#options) - [Validation errors](#validation-errors) - [Plugins](#plugins) - [Related packages](#related-packages) - [Some packages using Ajv](#some-packages-using-ajv) - [Tests, Contributing, History, Support, License](#tests) ## Performance Ajv generates code using [doT templates](https://github.com/olado/doT) 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 full JSON Schema [draft-06/07](http://json-schema.org/) and draft-04 standards: - all validation keywords (see [JSON Schema validation keywords](https://github.com/epoberezkin/ajv/blob/master/KEYWORDS.md)) - full support of remote refs (remote schemas have to be added with `addSchema` or compiled to be available) - support of circular references between schemas - correct string lengths for strings with unicode pairs (can be turned off) - [formats](#formats) defined by JSON Schema draft-07 standard and custom formats (can be turned off) - [validates schemas against meta-schema](#api-validateschema) - supports [browsers](#using-in-browser) and Node.js 0.10-8.x - [asynchronous loading](#asynchronous-schema-compilation) of referenced schemas during compilation - "All errors" validation mode with [option allErrors](#options) - [error messages with parameters](#validation-errors) describing error reasons to allow creating custom error messages - i18n error messages support with [ajv-i18n](https://github.com/epoberezkin/ajv-i18n) package - [filtering data](#filtering-data) from additional properties - [assigning defaults](#assigning-defaults) to missing properties and items - [coercing data](#coercing-data-types) to the types specified in `type` keywords - [custom keywords](#defining-custom-keywords) - draft-06/07 keywords `const`, `contains`, `propertyNames` and `if/then/else` - draft-06 boolean schemas (`true`/`false` as a schema to always pass/fail). - keywords `switch`, `patternRequired`, `formatMaximum` / `formatMinimum` and `formatExclusiveMaximum` / `formatExclusiveMinimum` from [JSON Schema extension proposals](https://github.com/json-schema/json-schema/wiki/v5-Proposals) with [ajv-keywords](https://github.com/epoberezkin/ajv-keywords) package - [$data reference](#data-reference) to use values from the validated data as values for the schema keywords - [asynchronous validation](#asynchronous-validation) of custom formats and keywords Currently Ajv is the only validator that passes all the tests from [JSON Schema Test Suite](https://github.com/json-schema/JSON-Schema-Test-Suite) (according to [json-schema-benchmark](https://github.com/ebdrup/json-schema-benchmark), apart from the test that requires that `1.0` is not an integer that is impossible to satisfy in JavaScript). ## Install ``` npm install ajv ``` ## <a name="usage"></a>Getting started Try it in the Node.js REPL: https://tonicdev.com/npm/ajv The fastest validation call: ```javascript // Node.js require: var Ajv = require('ajv'); // or ESM/TypeScript import import Ajv from 'ajv'; var ajv = new Ajv(); // options can be passed, e.g. {allErrors: true} var validate = ajv.compile(schema); var valid = validate(data); if (!valid) console.log(validate.errors); ``` or with less code ```javascript // ... var valid = ajv.validate(schema, data); if (!valid) console.log(ajv.errors); // ... ``` or ```javascript // ... var valid = ajv.addSchema(schema, 'mySchema') .validate('mySchema', data); if (!valid) console.log(ajv.errorsText()); // ... ``` See [API](#api) and [Options](#options) for more details. Ajv compiles schemas to functions and caches them in all cases (using schema serialized with [fast-json-stable-stringify](https://github.com/epoberezkin/fast-json-stable-stringify) or a custom function as a key), so that the next time the same schema is used (not necessarily the same object instance) it won't be compiled again. The best p