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Command line interface for ajv, one of the fastest json schema validators.

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npm install -g ajv-cli


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 mupltiple 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.

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 indentaion/line-breaks (for easy parsing)
    • text: human readable error messages with data paths
  • --changes=: detect changes in data after validation.
    Data can be modifyed 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 (using ajv-pack).

ajv compile -s schema
# compile to module (BETA) 
ajv compile -s schema -o validate.js


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

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

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

Only a single schema can be compiled with this option.

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

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

Migrate schema(s) to draft-06

This command validates and migrates schema to draft-06 using json-schema-migrate package.

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 mupltiple 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


  • v5: migrate schema as v5 if $schema is not specified
  • --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 (excluding migrate command):

Option Description
--data use $data references
--all-errors collect all errors
--unknown-formats= handling of unknown formats
--verbose include schema and data in errors
--json-pointers report data paths in errors using JSON-pointers
--unique-items=false do not validate uniqueItems keyword
--unicode=false count unicode pairs as 2 characters
--format=full format mode
--schema-id= keyword(s) to use as schema ID
--extend-refs= validation of other keywords when $ref is present in the schema
--missing-refs= handle missing referenced schemas (true/ignore/fail)
--inline-refs= referenced schemas compilation mode (true/false/<number>)
--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
--error-data-path=property data path in errors
--messages=false do not include text messages in errors

Options can be passed in either dash-case and camelCase.

See Ajv Options for more information.

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