5.0.0 • Public • Published


Command line interface for ajv, one of the fastest json schema validators. Supports JSON, JSON5, and YAML.

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npm install -g ajv-cli

JSON schema language and version

Parameter --spec can be used with all commands (other than help) to choose JSON schema language:

  • --spec=draft7 (default) - support JSON Schema draft-07 (uses import Ajv from "ajv")
  • --spec=draft2019 - support JSON Schema draft-2019-09 (uses import Ajv from "ajv/dist/2019")
  • --spec=draft2020 - support JSON Schema draft-2020-12 (uses import Ajv from "ajv/dist/2020")
  • --spec=jtd - support JSON Type Definition (uses import Ajv from "ajv/dist/jtd")


Help command

ajv help
ajv help validate
ajv help compile
ajv help migrate
ajv help test

Validate data

This command validates data files against JSON-schema

ajv validate -s test/schema.json -d test/valid_data.json
ajv -s test/schema.json -d test/valid_data.json

You can omit validate command name and .json from the input file names.


-s - file name of JSON-schema

Only one schema can be passed in this parameter

-d - JSON data

Multiple data files can be passed, as in -r parameter:

ajv -s test/schema.json -d "test/valid*.json"

If some file is invalid exit code will be 1.

-r - referenced schemas

The schema in -s parameter can reference any of these schemas with $ref keyword.

Multiple schemas can be passed both by using this parameter multiple times and with glob patterns. Glob pattern should be quoted and extensions cannot be omitted.

-m - meta-schemas

Schemas can use any of these schemas as a meta-schema (that is the schema used in $schema keyword - it is used to validate the schema itself).

Multiple meta-schemas can be passed, as in -r parameter.

-c - custom keywords/formats definitions

You can pass module(s) that define custom keywords/formats. The modules should export a function that accepts Ajv instance as a parameter. The file name should start with ".", it will be resolved relative to the current folder. The package name can also be passed - it will be used in require as is. These modules can be written in TypeScript if you have ts-node installed.

For example, you can use -c ajv-keywords to add all keywords from ajv-keywords package or -c ajv-keywords/keywords/typeof to add only typeof keyword.


  • --errors=: error reporting format. Possible values:

    • js (default): JavaScript object
    • json: JSON with indentation and line-breaks
    • line: JSON without indentation/line-breaks (for easy parsing)
    • text: human readable error messages with data paths
  • --changes=: detect changes in data after validation.
    Data can be modified with Ajv options --remove-additional, --use-defaults and --coerce-types).
    The changes are reported in JSON-patch format (RFC6902).
    Possible values are js (default), json and line (see --errors option).

Compile schemas

This command validates and compiles schema without validating any data.

It can be used to check that the schema is valid and to create a standalone module exporting validation function(s).

ajv compile -s schema

# compile to module file
ajv compile -s schema -o validate.js

## compile to stdout, to allow code formatting (js-beautify has to be installed separately)
ajv compile -s schema -o | js-beautify > validate.js


-s - file name(s) of JSON-schema(s)

Multiple schemas can be passed both by using this parameter multiple times and with glob patterns.

ajv compile -s "test/schema*.json"
-o - output file for compiled validation function module

If multiple schemas are compiled with this option the module will have multiple exports named as schema $id's or as file names, otherwise the module will export validation function as default export.

ajv compile -s "schema.json" -o "validate_schema.js"

-o without parameter should be used to output code to stdout to pass it to some code formatter.

This command also supports parameters -r, -m and -c as in validate command.

Migrate schemas

This command validates and migrates schema from JSON Schema draft-04 to draft-07, draft-2019-09 or draft-2020-12 using json-schema-migrate package.

The version of JSON Schema is determined by --spec parameter (only "draft7", "draft2019" or "draft2020").

ajv migrate -s schema

# compile to specific file name
ajv migrate -s schema -o migrated_schema.json


-s - file name(s) of JSON-schema(s)

Multiple schemas can be passed both by using this parameter multiple times and with glob patterns.

ajv migrate -s "test/schema*.json"

If parameter -o is not specified the migrated schema is written to the same file and the original file is preserved with .bak extension.

If migration doesn't change anything in the schema file no changes in files are made.

-o - output file for migrated schema

Only a single schema can be migrated with this option.

ajv compile -s "schema.json" -o migrated_schema.json


  • --indent=: indentation in migrated schema JSON file, 4 by default
  • --validate-schema=false: skip schema validation

Test validation result

This command asserts that the result of the validation is as expected.

ajv test -s test/schema.json -d test/valid_data.json --valid
ajv test -s test/schema.json -d test/invalid_data.json --invalid

If the option --valid (--invalid) is used for the test to pass (exit code 0) the data file(s) should be valid (invalid).

This command supports the same options and parameters as validate with the exception of --changes.

Ajv options

You can pass the following Ajv options:

Option Description
Strict mode
--strict= true/false/log - set all strict mode restrictions
--strict-schema= log on (log) or ignore (false) strict restrictions (the default is to log)
--strict-tuples= throw on (true) or ignore (false) strict schema restrictions (the default is to throw)
--strict-types= throw on (true) or ignore (false) strict types restrictions (the default is to log)
--strict-required= throw on (true) or log (log) required properties restrictions (the default is to ignore)
--allow-matching-properties allow properties matching patterns in patternProperties
--allow-union-types allow union types
--validate-formats=false disable format validation
Validation and reporting
--data use $data references
--all-errors collect all validation errors
--verbose include schema and data in errors
--comment log schema $comments
--inline-refs= referenced schemas compilation mode (true/false/<number>)
Modify validated data
--remove-additional remove additional properties (true/all/failing)
--use-defaults replace missing properties/items with the values from default keyword
--coerce-types change type of data to match type keyword
--multiple-of-precision precision of multipleOf, pass integer number
--messages=false do not include text messages in errors
--loop-required= max size of required to compile to expression (rather than to loop)
--loop-enum= max size of enum to compile to expression (rather than to loop)
--own-properties only validate own properties (not relevant for JSON, but can have effect for JavaScript objects)
Code generation
--code-es5 generate ES5 code
--code-lines generate multi-line code
--code-optimize= disable optimization (false) or number of optimization passes (1 pass by default)
--code-formats= code to require formats object (only needed if you generate standalone code and do not use ajv-formats)

Options can be passed using either dash-case or camelCase.

See Ajv Options for more information.

Version History

See https://github.com/ajv-validator/ajv-cli/releases






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