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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 with draft 6 support. [](https://travis-ci.org/epoberezkin/ajv) [](https://www.npmjs.com/package/ajv) [](https://www.npmjs.com/package/ajv) [](https://codeclimate.com/github/epoberezkin/ajv) [](https://coveralls.io/github/epoberezkin/ajv?branch=master) [](https://greenkeeper.io/) [](https://gitter.im/ajv-validator/ajv) ## Using version 5 [JSON Schema draft-06](https://trac.tools.ietf.org/html/draft-wright-json-schema-validation-01) is published. [Ajv version 5.0.0](https://github.com/epoberezkin/ajv/releases/tag/5.0.0) that supports draft-06 is released. It may require either migrating your schemas or updating your code (to continue using draft-04 and v5 schemas). __Please note__: To use Ajv with draft-04 schemas you need to explicitly add meta-schema to the validator instance: ```javascript 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) - [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) - 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) - [Related packages](#related-packages) - [Packages using Ajv](#some-packages-using-ajv) - [Tests, Contributing, History, 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 6](http://json-schema.org/) and draft 4 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 4 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-6 keywords `const`, `contains` and `propertyNames` - draft-6 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 var Ajv = require('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 // ... ajv.addSchema(schema, 'mySchema'); var valid = ajv.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 performance is achieved when using compiled functions returned by `compile` or `getSchema` methods (there is no additional function call). __Please note__: every time a validation function or `ajv.validate` are called `errors` property is overwritten. You need to copy `errors` array reference to another variable if you want to use it later (e.g., in the callback). See [Validation errors](#validation-errors) ## Using in browser You can require Ajv directly from the code you browserify - in this case Ajv will be a part of your bundle. If you need to use Ajv in several bundles you can create a separate UMD bundle using `npm run bundle` script (thanks to [siddo420](https://github.com/siddo420)). Then you need to load Ajv in the browser: ```html <script src="